Jasun

If you want to get the extra performance from 12th gen then it's worth it. But like I said, those cheap B450 motherboards are something nice. They're both worth it

That's fine, though if the deals they have aren't great you can always order the RAM/Storage while you're in store. There's not really a reason to go with something name brand, so just get whatever the cheapest 3200MHz CL16 2x8GB kit you can find, whether it be on Micro Center, Amazon, Newegg, etc. If you just wanna walk out of the store with a full system you can build that day though and are willing to take the $5-10 upcharge for a name brand kit, that's fine too. 
 
I still have no idea why PCPartPicker has that warning, that board was released after the 12400 was released, MSI would have been complete idiots in order to not have support for that chip in the release BIOS (they're not complete idiots, they've made some dumb decisions in the past but this is not one of them). 
 
So yes, the BIOS will be updated. You can also get the ATX version of that board, last I checked it was the same price as the mATX version, so you might as well get the extra expansion options for that board.

I wouldn't pay any more than $250 for it. If you're paying more than that you might as well get an RX 6600 for $330 that will be a bit faster. 
 
TBH for this budget, unless you're getting that card for dirt cheap I'd try and just get something else. 
https://pcpartpicker.com/list/Mrph78
 
This system would have a faster GPU, a faster CPU, and be all around great. The CPU is the price at Micro Center, the motherboard is $20 less but MC has a bundle deal where it's $20 off if you buy a mobo/CPU together, so it should be the same overall. 
 
Where'd you see equal performance? The 12400 is the same as the 5600, which is ~10-20% faster than the 11400. 

This review was published before the 5600 came out, but ganers nexus' subsequent testing showed that the 5600 has near identical performance to the 5600X so use that for comparison
 
Now the 5500 is a different story. I don't recommend going for that one.
 
When you compare $50 more, are you comparing the CPU and motherboard or just the CPU? Because there are B450 motherboards suitable for this CPU that are very inexpensive.

Are you getting a good price on that CPU and motherboard?
 
If you're not going for 12th gen Intel, a Ryzen 5 5600 with an inexpensive B450 motherboard would outperform this system. You could also save some money and get a better GPU, like a 2070.

stay away from A-series motherboards, the money you save on them is not worth the decrease in component quality. Any B450 should be fine as you won't need the features of b550 for the r5 3600, if you plan on upgrading to 5000-series cpu getting a x470 board might be worth it.
 
I noticed that your PSU isn't on the PSU-tier list so you might want to have a look at that too. (
 

We would need a budget if you want the most performance for your buck. The laptop you have chosen will perform very well in Warzone but in my opinion, I would never get that laptop because of how 'gamery' it looks with all those red accents. If you want something more subtle (but will run hotter), you can get the MSI GS65 or you can spend more money and go for the MSI GS66.

That's a laptop, highly unlikely you'll be able to upgrade anything other than the RAM (maybe)

Is his monitor plugged into the correct gpu?

Is his monitor plugged into the correct gpu?

Is his monitor plugged into the correct gpu?

Your priorities are in the wrong place. 200hz monitor with a 1660s, a 3600, that is also 2560x1080p? no. Don't do that. RGB mousepad? Couldn't you spend the money in a better way? Plus this is a new setup not computer. The RAM and Motherboard are kind of... Shady at best. This won't run like How you are expecting. a 240mm aio with a 3600? Please. Reconsider what you're spending your money on, this is not something you should buy

Have you tried remounting the cooler?
Dis you remove the sticker at the bottom of the mounting of the cooler?
Did you add enough thermal paste?
Is the mounting pressure good enough?

You shouldn't really be worried about your desktop resolution ruining your battery life because the resolution only contributes to how many pixels your GPU has to render and even with an iGPU, that should be no problem. I would look into any specific background tasks that may be running and optimizing windows for battery. 
General Windows tips for longer battery: 
- turn on power saving mode (battery icon, drag all the way to left side)
- lower brightness if possible
- close all unneeded background programs (taskbar -> up arrow -> right click -> quit/close)
- turn off any peripherals or keyboard lighting if applicable
- undervolting (only if you know what you're doing, dave2d has a nice video on how to lower thermals on a laptop [it also reduces battery usage to a certain extent])
- etc. (you can always find articles/videos online that tell you how to reduce general battery usage on a laptop)

You shouldn't really be worried about your desktop resolution ruining your battery life because the resolution only contributes to how many pixels your GPU has to render and even with an iGPU, that should be no problem. I would look into any specific background tasks that may be running and optimizing windows for battery. 
General Windows tips for longer battery: 
- turn on power saving mode (battery icon, drag all the way to left side)
- lower brightness if possible
- close all unneeded background programs (taskbar -> up arrow -> right click -> quit/close)
- turn off any peripherals or keyboard lighting if applicable
- undervolting (only if you know what you're doing, dave2d has a nice video on how to lower thermals on a laptop [it also reduces battery usage to a certain extent])
- etc. (you can always find articles/videos online that tell you how to reduce general battery usage on a laptop)

We are not the ones to tell you which case you should buy. Most cases nowadays at that price range are pretty good in terms of functionality, so just go out and buy something you think looks good

That black bracket on the second image can come off via the screw on the right 

Probably not but the easiest way to find out would be to test the mouse. 

Thanks!  It is prominently displayed in my apartment and my wife approves of these colors, so these colors it will remain.  Although she has no idea what she is looking at and thinks I am crazy. 

There shouldn't be any conflict. Maybe a minuscule CPU degradation due to it scanning the temperatures through two different programs instead of one but with CPUs nowadays, that should not be an issue at all. 

~800 USD can get you a laptop with a GTX 1050Ti and an i5 7th gen/i7. It isn't really hard to find those around Amazon but their quality cannot be compared to higher end ones that are more expensive because of their extra features, etc. If that's what you call budget, then go ahead and browse Amazon to find one of these but other than that, there are quite a bit of videos that Linus has done over these laptops (and other tech YouTubers) so I would just hop onto YouTube and find videos that meet your criteria and then judge  based on the videos' review. I know this sounds like shitty advice on what laptop to get but I would think that looking at an actual video with images will spark your interest, rather than people telling you what to buy, and of course, you can look at other suggestions posted here and search them up on YouTube to see if you actually like them. 

welcome to the Linus Tech Tips forums!
 
kinda open-ended question.
can't make any best suggestion with your limited information provided
what 'cha using the PC for?
if gaming what resolution?
streaming?

70 bucks and 15 mbps? switch right now lol. I have xfinity and I pay for around the same for 70 mbps.. 

An old but reliable cooler would be the Hyper 212 EVO from Cooler Master. You can find these on Amazon for ~30 bucks 

On the official intel site, the temperature for that specific cpu should not exceed 72 C for normal usage... What cooler are you using?
 
Edit: Woops, stock cooling... Maybe you should invest in a better cooler?