I faced the exact same situation a week ago when too many users are trying to add multiple rows at the same time to the Sheet.
It created a hell of a delay and as I was using a relation for some conditions, it did not work at all.
I had to utilizie a user-specific column as my condition to keep it inside Glide, before the rows are actually written to the Sheet. Not sure if it helps your case but aside from moving to Glide Tables, that’s my solution for now.
My most important use case was that participants upload pictures only from their cameras so I switched to Glide Tables. We had lags of upto a minute only. So much better than Sheets though.
The event went well! I also found a way to bulk download all the images that were uploaded on Glide Tables.
Will do a thread about that soon.