I am traveling with a group of 16 shortly and, let me tell you, haven't traveled yet, but so far the various accounts have been a NIGHTMARE for me to get straightened out. Last year I went with 2 rooms booked and used one account and no issues. But it was just me, DH, DS, and my parents in their own room. My DS and I were the only ones really using the app.
This trip, it is a cast of thousands. I already had my account, my DS did have an account from a previous trip on his own, and my other family members who booked on their own really did need their accounts, but we are having some ADRs together.
The problem came when we booked the rooms, the CM apparently input name info into the Disney system. When I logged in and added friends/family before some accounts were made, I got a kind of "dummy" profile. The problem has come up later when some of them created their own accounts. Then I had duplicate profiles and the "real" profile was now the one they set up on their own so none of the ADRs and reservations were showing for them. It's taken me quite some time to clean it all up and I am still having an issue with some of my daughter's plans.
I think multiple accounts work fine but you need to be careful linking stuff if there is more than one profile in the system.