Not quite.
It's pre-boarders who need assistance (that would include the OP), then A1-A15 which is Business Select and despite the name anyone can purchase these although there are of course only 15 of these per flight. You can however purchase Upgraded Boarding at the gate which for a nominal fee that varies per flight (usually $20-40 or so sometimes up to $60) you can purchase a Boarding Position in that A1-A15 should there be any left.
Then you have A16-30, then A31-60. After that it's A-Listers (regular and preferred) who did NOT get an A Boarding group I can only guess that is the preferred status folks you're talking about but even being an A-lister does NOT guarantee A-Boarding group. During the pandemic SWA did enhance the A-List by allowing those booked on the same confirmation number as the A-lister to board with the A-lister (they usually do it now by just assigning consequential Boarding positions like A24 and A25) however if you aren't on the same confirmation number that benefit shouldn't apply (that means those who have a Companion pass will not be boarding with their A-lister unless they are also an A-lister themselves as Companion passes have to be booked separately). That added benefit however can def. add more people boarding the plane earlier on than before.
Then you have active military and Family Boarding (allows for 2 adults with a child 6 and younger). It's been reported that especially to/from Orlando Family Boarding has a higher chance of being suspended because of the sheer amount of kids on that route but it certainly occurs often enough.
Then you have B1-30, then B31-60, then finally C1-30 and C31-C60.
Purchasing Early Bird Check-In (EBCI) automatically assigns a Boarding position at 36 hours in advance but is behind A-Listers who are also assigned at 36 hours in advance. Those who purchase Anytime Fares with EBCI are given priority over those who purchase WGA with EBCI. It's easy and complicated at the same time. EBCI should not be looked at in a preferred status way. It's something someone can do just 1 time or every time, up to them.
You're def. right about trying to locate seats all together and it's usually a question that comes up time and time again about people flying with their children. There is a dedicated SWA thread that has chronicled this over the years.