yes, first is a good way to boost PQMs. You can usually earn 2x PQMs on most domestic first tickets. Don’t forget the 500 PQMs either, so even a short flight would give you a minimum 500 on economy or 1,000 on P fare or higher.
Provided you're careful to upgrade by calling in and buying up to a first class fare. If you accept an offer from the website after booking, you may or may not get bonus PQMs.