I have multiple online accounts and sometimes when I work with different organisations I have different one-drive and google drive accounts I need to use. Most of the official clients do not support multiple accounts on the same machine. Are there any good alternatives?

Organising files and videos is less important when working on your own, provided you just want to keep creating new content. If you want to work in a team, or revisit videos and edit them or transcribe them, then you need to organise.