Several years ago our old forums (phpbb3) were hit with a big wave of bogus registrations, many of the emails were similar to the gmail ones you listed, though we also got quite a few from .ru addresses, notably yandex.
At one point we were getting 1000 of them a day. By the time we got it under control, we had over 80,000 bogus records.
We solved the problem by requiring a valid current membership ID (our membership system was totally separate) which had not already been used to create a forum record. That way even if someone had access to our membership records (they’re online) they could only use an ID once. Bogus registrations fell to essentially zero.
I’ve not used the data explorer enough to know what its limitations are. I’ve been a postgresql DBA for over 20 years, so going directly into psql has not been an issue for me, but I’ve limited my activities there to read-only queries.