This may or may not be a problem specific to your own installation though. While I don't have 100+ tabs, I've been using quick commands for everything since I started using Vivaldi without any issues - it is very snappy for me.

Could be. I've noticed it slows down more when you have a lot of bookmarks. Ideally you could choose what type of results quick search would return. I'd be perfectly happy only searching tabs and commands.