The backside can get hot. With my previous setup (before mounting it), the backside is facing up exposed to open air, but it’s still very hot at full load. There is no performance issue though. I guess it’s designed like this and it’s totally normal.

Good question, it's mererly because I was using an ITX case with those hardwares, but it's not easy to fit the case behind the TV, so I came up with this solution. If I start new, I might choose ATX instead

Only a video cable + a wifi antenna for now. The power cable is on the other side and is hardly noticeable.

Thanks! I can still see it from the side lol

CPU fan can get noisy at full load. Could use a better cooler, this one is just what I already have and is okay so far

Yeah IKEA also has a gaming line, however nothing about a gaming PC

There is a 20mm space from the GPU’s backboard to the pegboard, should be enough