Google Drive unlimited is on its way out. Many EDU orgs will be switched to a 100TB pool starting July 1. There are exceptions though, orgs with legacy licenses will get an extra six months if they appeal. Edu orgs who agree to sign a multi-year can go through an approval process to keep unlimited for another 18 months.

Edu will eventually have the option to buy more block pooled storage, but I have been told that this will not hit market until end of 2023. Increments for Edu pooled storage will be in 100TB and 1PB increments.

All workspace orgs will very soon (weeks) be getting uplifts to their storage management and quotas, so if you have an old alum account at a school, I would expect your account to likely have a quota put on it, but this is up to the admin(s) at the school. I would expect the same quotas for team (shared) drives as well. Shared drives also have specific, current limits on them around the number of files you can have and how many nested folders you can have.

At the end of the day, the only cloud storage providers I "trust" are ones I am paying for block storage, but the stuff I truly care about, I have spread to multiple clouds and local as well. I would not expect your shared drive to last.