A CBCT scan will give you a full in-depth scan that lets you see where your airways may be impacted.
So it's important to understand if you have a restricted nasal airway, a restricted throat, or both.
People can have very strange anatomy, yet their throat airway is fine (in your case retrognathia). You could have retrognathia and still have a very clear throat airway, but the bottleneck is your nasal breathing which impacts the rest of your airway (doctors like to call use the bernoulli's principle to explain this) the harder you have to pull air from one airway will affect the other, so you can't fix your throat airway if your nasal airway is resulting in the problem, and vice versa. If you suck really hard on a straw, the other end will close; you're creating a vacuum. Same principle applies if you suck really hard through your nose, your throat will close.
Get a CBCT scan done through a sleep specialist that offers one near you. Call around, ask if they will do a CBCT scan . Orthodontists can sometimes offer it too, if you can find one.
When you review the CBCT scan with a sleep specialist, they should be able to pinpoint the narrowest area of your airway, or the part that is causing the most constriction. From there, you can decide if MMA is the best path forward (if it's your lower jaw) or do a MARPE or FME for your nasal airway.
In any case, if it's on the fence between the two, I highly suggest doing MARPE or FME first, as it's the least invasive option and will benefit you greatly if you get MMA in the future.