Hi eerikitect ,
I had the exact same thing happening on my old PC. 3.0 (CyclesX) was ten times slower than 2.9. This appears to be, because my GPU wasn't supported (already since 2.7something, I think) and CPU rendering is very ineffective in CyclesX.
As soon as I got a new Computer everything worked; Cycles is a lot faster than before 3.0! It is not only the amount of RAM on your GPU, but also its age.