What would be a good way to store an online backup for my wallet then? Maybe uploading it to Google Drive, or MEGA?
This will only make things worst . Keeping your wallet Online is the worst idea you can get mate .
Hacker don't need to hack your PC , he should simply hack your Gmail or MEGA Account (not even hacking probably simple Brute force cracking) and he is in .
I suggest keeping them in Offline device .
~ Madness