would this case fit this build?
yes
Also Is this probably best build on here?
i'd probably be more biased towards my spec above.
reason being - 1600x doesn't come with a cooler, so you'll need to budget for one too.
2600 trumps 1600x in games - due to generational improvements and newer self-overclocking algorithms
16gb ram in my spec
asus prime b450m-k is a terrible motherboard
580 4gb is half the vram compared to the spec above, but as i said - "rx580 4gb for £150. anything higher and getting a £200 nvidia 1660 is the better choice. for £150, this is priced right."
and for 1080p gaming, 4gb is sufficient for the life of the card.
also, VA panels are notorious for being very smeary with fps games, especially the cheap ones. better to go for a solid TN panel instead. also the rx580 probably wouldn't be able to run the panel at it's full 144hz refresh rate. 75hz is probably the sweetspot between price/performance.
in conclusion, this would be my recommendation now (added your proposed case):
My basket at Overclockers UK:
as my prior build, i haven't specced parts that you can get cheaper elsewhere. for the rest of the parts, ocuk are price competitive.
namely:
1) ryzen 2600 (part number: YD2600BBAFBOX) for £147.20
2) corsair 16gb 3000mhz RAM (part number: CMK16GX4M2D3000C16) for £84.89
3) corsair CX550M (part number: CP-9020102-UK) for £55.15.
all these 3 components, again, can be bought at the same place - and has free shipping.
total build cost = ~£755