If you want to use an older version, you can find them all here.
You can also install multiple versions by just naming a different folder for Shotcut to go into.
The only real risk of using multiple versions is not having your projects work correctly between the different versions.
If you’re on Windows 10, one thing to consider is Windows might be downloading/installing updates in the background. I’ve got a fairly good computer as well and it just makes my computer real slow as well. Each time I forget windows does this then I go to restart and get the see the update in the shutdown menu.
You could also try changing your Display Method.
Providing great detail on the bugs you’re experiencing is the only way the bugs will get fixed.