Google Drive has some pretty hard to understand semantics when it comes to sharing folders and files. When a file or folder is shared with you, they are not synced to your desktop, they live in a special place called ‘Shared With Me’
So they do not take any of your disk quota (much better than Dropbox), but they do not sync down with you use the Google Drive client for Mac or Windows. You can edit them to your hearts content. Note that with Google Apps (now called GSuite), you never actually download any data, instead you get a tiny file which points to data in the cloud. This is nice because you can rename the files to your hearts content and Google doesn’t get confused.
In contrast, Microsoft OneDrive does copy the real data down and if you rename things and then sync up, you can get in real trouble. Because it has to figure out what files are actually different.
As an aside with GSuite, the way that offline viewing is done is that the actual data is cached in the Chrome browser and so you never actually manipulate the files, just pointers. That makes it really hard to setup because you have to remember to enable offline for each Chrome and then each document, but it works better when there are multiple copies since only GSuite code manipulates things.
Finally, if you want to make a shared folder act like a regular Google folder that is owned by you you have to do something very special which is to use the web browser right click on the files or folders in Shared with me and select “Add to My Drive” so it now count in your quota and get synced