I only went a little over my 10GB hot spot limit for my first month on the new plan and the first without T Mobile’s coronavirus related unlimited data upgrade. I did not do any (that I remember) video streaming and moved more of my casual web browsing to my phone, since that no longer counts toward my limit. I used almost 5GB
I had upgrade to their “Simply Prepaid Unlimited Plus” plan with the expiring unlimited upgrade. It only slows to 3G speeds after hitting the data limit instead of 2G like the cheaper plan. I noticed the 3G speeds for probably less than a day, which probably wasn’t a great test, but I can say it was much better than the 2G throttling. It was a bit variable, but seemed usable for regular web browsing, server administration, and file editing, which are the most important things.
I’ll keep going with it unless further testing proves it inadequate or I go back to working at the office.