1. that GPU looks really expensive but that is to be expected, plus its a pretty darn weak card, its a potential bottleneck (depends on you usage though).
2. ABSOLUTELY, that I5 is overclockable yet you have a B560 motherboard which won't allow you to overclock, the I would look for another GPU (a 1060 6GB would do)
3. You won't need a wifi card if you plan to use an ethernet cable.
4. alling the cpu properly without touching the bottom, allign the ram sticks properly, make sure you apply enough thermal paste and tighten everything in a cross pattern.
5. Make sure you cable manage things propely since down the road changing components will become a head ache because the cables would be in the way. That's all I can think of right now.