For my experience with their B738 and -MAX fleet:

At the gate boarding will be started on groups and what I have noticed on many flights:

Pax with special needs with an order like wheelchair etc.
A - Flex ticket and purchased priority boarding.
B - families and front of the aircraft
C - exit rows and rest of the pax.

Purchase group A, if you are sitting on first row where overhead space is limited (mostly row 2 have more space and you avoid getting your stuff overhead rows 5-13).

Be at the gate early. If you come later, your group A have already announced. They will wait only couple of minutes. Then all the rest pax are called to board the aircraft.

Some flights leave from tarmac, so boarding groups are useless when bussed to the aircraft. One precise route I use, I already know which weekday that flight leaves from tarmac as others leaves from gate. Monitor your departure airport on weekly basis if that is important to know (some gates are only for bus transfer depending of airport).

Priority boarding is good only when aircraft is ready to board.

Sometimes group A and B pax awaits on the tube for aircraft to be ready to board. You at least get you stuff for overhead bins.

If you are sitting on exit row, there is no need to purchase priority boarding as crew standing there is monitoring overhead lockers; mostly at least one is closed for exit row pax only. So you will get you hand luggage there in most cases. They mostly ask me kindly am I exit row pax.

That is all I know. I don’t understand group B and those pax sitting on rows 2-13, mostly families and some elderly couples.