Darprix

I had a MSI MAG24C and no problem with it.
 
The ASUS and AOC should be some nice choice

Overall, it's a strong combo. A good i7 and a high end graphics card will work out, you could go with a 2080ti even and be fine.

as long as the mounting spots are the same (all fans should be) then yes. you can switch them. 

Both are rock solid motherboards, the 50 bucks more expensive though is for full enthusiast that might go with full exotic cooling like mineral oil or Liquid Nitrogen for super overclocking.
 
While the other cheaper board may not have few welcome extras in those cases it will have every thing you need to run an i9 9900K at 5ghz off it with the right cooling and PSU.
 
Both looks quite nice too!

the cheaper one has a slightly cheaper vrm (still overkill for a 9900k) that runs a bit hotter, it also doesnt have a single bios mode that results in a faster boot on gigabyte boards, and, the master has an extra clear cmos somewhere, whether it's worth 50usd is ur personal preference.