I have the same issues, for some reasons VTuberPlus after a few minutes starts to eat all my RAM available, I don't know why, I haven't changed anything, I updated my drivers, rebooted, etc, but the software is just causing me severe lag, and while playing games and streaming, I cruelly need my RAM.
You might be using some unoptimised custom items. Everything that you have in your UserItems folder will load in your ram as soon as you start the program. I recommend checking your items and see if there's anything that's eating up your ram. Also I recommend disabling "Auto Reload Items" in General Settings.