A major issue we we have affecting this in Africa is the latency and lag to mining pools overseas. Lag reduces mining profitably. Use
https://minerstat.com/mining-calculator to check current profitability from each pool and then check latency. I switch between HiveOn, Poolin and Binance for the best profits.
I don't think it would be worthwhile with the current prices of GPUs unless you get bargains or 2nd hand. Too risky. It could take 9 months or more to pay off a rig like mine instead of 4 months when I bought it.
With Asus B250 you can mix any 13 cards, but slots 14-19 must be Nvidia P series mining GPUs. I use MSI B360-F Pro - Any 19 GPUs supported.
3060 can only be used in the main PCI-E x16 slot and wont work on a riser card, plus it only works on Nvidia v470.05 Windows drivers. You're looking at 48MH/s stable.
5700XT and 3060Ti offer the best ROI.
HiveOS (Linux) is way better than Window for mining.