Yes you should be able to send PM’s once you hit trust level 1.
The 20 minutes is actually timed by the system, and need to be on 5 different threads with 30 different posts. (Yeah a bit of a nuisance, but it is an effective automated way to vet hundreds of new people)
If you want to go back to a mailing list there is an option for it. You can see the instructions for it here -> Help! How do I get the mailing list setup in Discourse?
The issue is that if you use mailing list mode your trust level won’t increase as the system cant see how much reading you do. As long as your level 1 I dont think itll hurt anything.
I havent heard of anybody using the mailing list option yet, so if you run into any issues let us know.