Hi there!
I took the DAT yesterday (6/15). Probably the biggest difference is that I was NOT given graph paper for the PAT - when I asked, the Prometric employees informed me that in order to prevent the spread of COVID-19, they are not administering the plastic graph sheets that are traditionally given. I can't say if this is the same for every testing center, but I would definitely be mentally prepared for that. I studied the entire time relying on graph paper, and panicked a little when I was given blank paper.. it made hole punching much harder.
In my opinion, DATBC and Destroyer are both super valuable resources, but the real exam is definitely much more similar to DATBC. ESPECIALLY for the reading, general chemistry, and PAT sections.
Regarding the mask, most centers should allow you to bring in your own mask, so I would recommend taking your last practice test or studying for a few hours with the same type of mask that you will be wearing during the real exam. In my opinion, it made no difference at all, except for my glasses fogging up once or twice. Believe me, even if it feels a little strange now, the adrenaline will kick in during your exam, and you probably won't notice it at all.
I can't really say how difficult it was because I've only taken it once, and I don't have anything really to compare it to. However, I would say difficulty level is generally similar to DATBC, except for the PAT. In my opinion, the PAT was a little bit harder.
Best of luck! You're going to rock it! 🙂