ChusanaR.

I will be caution when I upgrade the GPU then. xD

Regional pricing can be a b*tch when considering upgrades, 12000TBH being about $350 USD which is close to the current $331 USD pricing. 
 
5800x3D trades blows with Ryzen 7000 non 3D and Intel's 13th generation, however you'd need to spend A LOT more to get comparable performance since it would require a new motherboard and potentially RAM. The closest thing on Intel's side to match pricing would be a 12600kf and budget DDR4 LGA 1700 motherboard, which gets beat by the 5800x3D by a sizeable margin. Ryzen 7000 would require new RAM, which immediately puts it past $450 USD.
 
Just to over-explain the scenario of why the 5800x3D holds its ground in your scenario. Just keep in mind with a future GPU upgrade that you'd want a full 16x card, so NOT cards like the RTX 4060, RTX 4060ti, RX 6600, RX 7600 which are all PCIe 4.0 8x for some reason.

Yes, yes it does capable. By default, CPU for DDR4 is capable up to 3200Mhz, even if you purchase the highest Zen4 AMD CPU (e.q. 5950X)
So it's up to Mobo to overclock XMP/EXPO to higher speed
And the good news, your ASUS B450-F mobo is capable of running 3600MHz and even higher if the RAM is capable to do more.
But for Ryzen CPU, going higher than 3600MHz is point of diminishing return, so better to save your budget on other components
Upgrade the RAM would definitely increase your gaming performance, but it wouldn't be game changing. Probably 5-8% at the very best scenario.
 
Since DDR4 RAM is 'discontinued' for current gen of CPU, it means that it will get cheaper as time goes on
So it's a good time to upgrade to 3200 or even 3600MHz, but try to always check the prices on Thai market place, because the price drop isn't always in line for each country
 
Yes, RTX 2060S is capable of running 2 monitor simultaneously
You can even run 3 monitors if you want
 
In addition, in the long run you may also consider to upgrade your 3600X CPU to 5800X3D for gaming focus (since this is the "last"-ish and best CPU for Zen4 platform)
But try to wait till next year or two until the price really drops hard, since it is still a popular CPU in the market
 
So the main focus for your upgrade should be monitor first, any of these brand you suggested would do fine and a jump from 75Hz to 144Hz is incredible, unless you're a content creator that wants super detailed and accurate colour

Thank you, I think I better save up for a better board and CPU then. bc better Board and CPU at this moment are gonna exceed my limited budget. from what I see over here the 5800X3D is about 12000THB (and I have to get a cooler too). Thank you for the idea 😄

They'll eventually fix them, but yeah wait at least two months after receiving miui 12 or just flash xiaomi.eu

There is no sign of it coming any time soon. Better install a custom rom or xiaomi.eu because the first miui 12 releases are generally really buggy. Dunno why they're using buyers as beta testers.
Coming from someone with a redmi note 8 pro.