A few things come to mind. Firstly if you cut some long layers it will give the illusion of not so overwhelming hair. Sort of puzzle piece cut like Devachan does it.
Barring that and airdrying I do notice my hair has less volume if I diffuse upright and press the diffuser toward my hair against my head rather than cup the hair at the bottom. I do that except for the bottom parts.
Be careful after scrunching out any crunch not to fluff too much. Also some ingredients cause more volume like wheat proteins and aloe but of course everyone's hair reacts differently so that part is trial and error.
A good conditioner and leave in will keep the curls clumped together more and make your hair seem less volumous. STiffer gels tend to do that for me personally too.
I'm sure some others will have ideas, I think your hair looks great but I know long hair can get to be overwhelming