I’m sorry, if my posting seemed ambiguous - I don’t like to give specific recommendations based upon less than complete familiarity with the application. Hence my “cautions”.
My intent, however, was NOT to disparage AGM batteries, in any way. I think they’re great - their principal disadvantage being cost.
Given the time (of which I’m short), I could offer is “caution list” on “Flooded” (or any other) batteries that would cause wonder why anyone could possibly contemplate their use.
I’ve installed 6V Flooded “Traction” Batteries (Trojan T-105 / T-125) on all of my previous boats; but will likely use AGM’s on my next boat.
There is no escaping the cost, though - especially if you’re looking at a new Charger and Alternator regulator (which do have value, even with flooded batteries, on their own merits).