I got a pack of 3 glass protector from Amazon and after installing the first one the tablet became very laggy. Saw your post here and the manual does indeed say not to cover any of the front sensors with a protector. These only have a cutout for the camera. So I took it off and the tablet was still super laggy. Decided to install the second protector and do a factory reset. So far the lag seems gone. I won't say it's a permanent solution until I've spent more time with it, but I'll report back if the lag returns or not. As much as I hated doing a factory reset so soon after getting the tablet, if it fixed the problem I'll be happy. But yes, it seems covering the sensors can affect this thing.
EDIT: So far things are still going smoothly today. Have everything restored from the Smart Switch PC program and set back up. Have restarted the tablet a few times just to check even. So it seems the factory reset fixed my problems. Don't know if it matters or not, but just to be sure I did my reset from the recovery mode. So my advice for anyone that runs into issues after installing a screen protector is to back everything up, with your on device cloud options and the Smart Switch PC program imo, then factory reset and you should be good to go.