I ran into the same problem last year when juggling several client Dropbox accounts on my Mac. What really helped was using a file manager that lets you connect multiple Dropbox accounts at once and move files directly between them, almost like copying between folders on your computer. I found a detailed guide about this setup here:
https://commander-one.com/dropbox-client-for-mac/. It explains how to link different Dropbox accounts and manage transfers more smoothly. Ever since I started using it, switching files between accounts feels way faster and I don’t have piles of temporary downloads on my desktop anymore.