GPU, but you should do both anyway as MC is also CPU-heavy.
The fix is to update it. You shouldn't downgrade as you're already on a driver version that's over a year old for this issue to occur and has long been fixed. Downgrading further will cause stability issues and significant performance drops.
There are no plans to workaround the issue in Forge as people are encouraged to upgrade away from a known old buggy driver.
Make a system restore point just in case, then follow the guide in the FAQ.