"Apex shouldn’t force or reward one playstyle over another."
Agreed. But solo queueing is not what I would call a playstyle. If you want to work the system to get the most points possible then you really have to work with a set squad as much as possible. If you don't then you have to make your peace with the fact that you're going to leave some cash on the table. So to speak.
"My understanding is that mmr affects match making in ranked but not the final rank points earned or lost in a game."
Yes and no. They may not be directly related, but there is a self-reinforcing synergy between the two. At any rate, there are a million little discrepancies and contradictions in the way the game measures your skill, the ways it uses those measurements to match you, and the ways it chooses to reward or punish you in the context of a ranked match. If you're looking for it to be one single cohesive and comprehensible whole, then you look in vain.
If you're really determined to take the rank grind that seriously then forget about your mmr and play ranked matches strictly by what is being rewarded in the particular season at hand. If you're concerned that those behaviors will artificially inflate or deflate your mmr and hence affect the quality of your matchmaking... well, let's just say the quality of matchmaking in this game is so atrocious that it won't matter either way whether the game thinks you're better than you are or worse than you are. Your matches will always be imbalanced, and playing in ranked, where matchmaking should in theory be very tight, is in reality no different than any two-bucket pubs match. So relax. Have a beer. Don't worry so much.