I just built my first rig last week. Before jumping in I tested/learned with my gaming rig and my deep learning rig for a few weeks. I am building a vega rig - I have 3 and a fourth is coming this week.
I researched video cards specifically looking at ROI. I used the monero benchmarch site to compare hashrates for different cards
GPU & CPU BENCHMARKS FOR MONERO MINING! and then a mining calculator to figure out potential daily/monthly profits. So for me the Vegas were by far the best ROI - with a 2000 monero hashrate they were looking like 3 months to be paid for. That doesn't include the potential rise in monero or whatever coin you mine.
I too have switched to AEON for now because the difficulty is so high on Monero - although I don't understand yet how to calculate how high is too high - I'm trusting the experts on this forum and learning from them.
Oh and also - my electricity is only 6.5 cents, and if I pay my bill early they chop 10% off my bill - which helps a lot.
I went GPU route because its so easy, the only cpu I would do would be the epyc route - but I've been watching and they aren't really available yet that I can find.