Sreno1

Some games use over 8GB of RAM. Not even a question, 8400 with 1440p panel.

8700 will do fine for streaming and you won't require a more expensive Z series motherboard. Make sure you get 16GB of ram

What's more likely is that OP isn't well versed in PC components (based on his PSU/RAM choice), and doesn't know that the 1030 is not good enough for gaming. If he was just browsing or doing low-intensity tasks no GPU or APU would be needed. It depends on the price he can find a motherboard, usually, Intel boards are more expensive, and with the 8100 being Coffee Lake the current board selection is limited. The 2200G might actually be the cheapest option when compared to the other options being the 1300x/i3-8100. All three perform within 10% of each other but the 8100 does have a substantial single core speed which is important for gaming. http://cpu.userbenchmark.com/Compare/AMD-Ryzen-3-1300X-vs-Intel-Core-i3-8100/3930vs3942

The 2200g APU is horrendous, as a CPU itself it's decent. But that makes it undesirable as the 1300x exists. Don't pick low-quality power supplies, PSU's determine the reliability and that is seriously something you don't want to mess up. https://pcpartpicker.com/list/ZHy68Y Overbudget but I think it is what you need to get a good value.

People who think more RAM correlates to better performance are showing their undeveloped knowledge regarding computers. I will admit 8GB is getting outdated in a few games, but 12GB surely covers everything you would be playing right now.

If you're getting a K series processor than you need a z series motherboard. Z270 I believe for Coffee Lake. 8gb or 12gb ram is enough for gaming atm. That AIO is of questionable quality, get a good air cooler from Noctua or Be Quiet for about the same price. You need to get an SSD in this build, you put your operating system on the SSD to make everything feel snappier. You can also opt to put games on the SSD if you have space, this will make those games load faster. I would say don't get the 8700k, its unnecessary for gaming and you can save a good bit of money. (seems you already realize you don't need an aftermarket cooler with the 8400, although you could to solve noise).

Where are you from? Do you have any parts already? Do you have a monitor/other peripherals? $800 budget is limited for your use case, as far as I know, simulations and modeling are resource intensive.

Will you just be gaming? Do you need peripherals? Base build with monitor and OS: https://pcpartpicker.com/list/2Ynqmq

you're paying for reliability, if you want to skimp out on this part then you can get the MSI board I recommended or an even cheaper b350.

Maybe this one? https://pcpartpicker.com/product/ZHyxFT/asus-strix-b350-f-gaming-atx-am4-motherboard-strix-b350-f-gaming When I picked the MSI board I was going off the pcpartpicker reviews, and it was among the mobos with the most, and best reviews.

https://pcpartpicker.com/list/9h7XyX This build will destroy 1080p 144hz, and work decently for 4k gaming on a TV.

Do you already have the 4k monitor? If not, you shouldn't be expecting that performance with that budget.

What's your budget? Where are you from? What is your use case? Please read the stickied thread(s) regarding the format for build planning Here's a baseline build for you to look at, your current spec is just the best thing you could find from AMD. https://pcpartpicker.com/list/tpJVw6

When considering upgrading, you need to ask yourself what you really need/want for your system setup. Instead of buying a new graphics card when your current one does the job, look at your mice, keyboard, monitors, chair, desk, etc. and see if you can upgrade your setup in a more worthwhile way.

How much were you planning on spending on a cooler? The air coolers I suggested will perform similarly to the AIO's. For example, I have my 6600k OCed to 4.6ghz with the smaller version of the Dark Rock Pro 3. Other good coolers that are less than $50 include the Scythe Fuma, Scythe Mugen, or Cryorig H5 Ultimate