Hello, thanks for the advice. Going to try this tonight. Had to download 300Gigs, after an hour 30 were done and speed was 800 bytes per second. So this seems promising.Have found the (workaround) solution. TLDR: read last paragraph.
Forget about downloading your files via the browser. I've tried multiple methods to no avail (even moving all my files into one folder and downloading that folder as a singular file). OneDrive's zipping speeds bottleneck your download speed.
What worked for me was downloading all your files via the OneDrive app that you get from the Microsoft Store (Get OneDrive - Microsoft Store). For some reason the app doesn't download a "zipped" version of your files but instead syncs them one-by-one onto your designated File Explorer folder. Sync speeds match whatever internet speed you're on. At least for me I was able to download 1.8GB worth of files in a minute (which is how its supposed to be with my ISP speeds).
Hope this helps!