Have you seen your Google Drive storage goes up the roof, yet you are only syncing a fraction of it with 100% sync selected?
Again, not the first time the Google UI gets confusing, intentionally or unintentionally. Here, intentionally I meant maybe it's by design so you end up paying more storage than you should
Look at my example (see banner image), before I checked today, I am warned that I'm using up >90% of my 200 GB subscription plan. My Google Drive has <50GB when all synced... where are those hidden GBs???
First you probably should check your Google Photos, where Google tries to make you auto-sync with all your devices. https://photos.google.com/
The other hidden usage you can find is that if you install Backup & Sync to your laptop, Google will try to ask you to sync your Desktop, Downloads, Documents and Pictures folders automatically (on a Mac). You can find it all here: https://drive.google.com/drive/computers
There is a management tool that Google provides, which I didn't find the link until I read some help articles from a Google search! This page will show you the storage usage break down: https://one.google.com/storage
To manage it, go to this link: https://one.google.com/storage/management
In my own case, there are >100GB in the Trash and it is still counting against my quota! When I thought it's a matter of simply clicking "empty trash" and it should be done, Google this and you shall find that many other have encountered issues just like I did. The empty trash function doesn't work when you have a huge amount of files there!
I still haven't found a working solution that I'm able to empty all the contents in Trash. So I have to pay double the price for the Trash contents until Google fixes it! If you know how, please tell me in the comments!