You should try to backup them to another cloud storage service like Mega, Dropbox, Box or Mediafire so you don't have to download or upload them again if some mishaps happen.

The best way is to use transfer services like Multcloud or Cloudsfer. Don't worry it's safe I've been using Multcloud for more than 6 months for my own personal collection and I think it's the best among 5+ services I've tried. No security problems so far. It has tons of free bandwidth enough to transfer GBs of videos to multiple storage accounts. Just don't forget NOT to "sync" them so if the source (google drive in this case) got deleted the files on the other account wouldn't get deleted too.