Well, I have the same Problem, Opera GX is extremely slow, Buffering Videos on YouTube etc takes hours. No there is definitely enough RAM and other resources on my PC available (32GB RAM, i7-11700K CPU and extremely good net speeds) also I already turned off VPN, Hardware ACC and some other things that could influence it, but still it takes more time than any other Browser I ever used.
So what else could be Reason for this slowdown, what else can I do to fix this Problem that shouldn't even exist in a "Gaming Browser"?