Jamie, an AGM battery IS a "lead" battery, and you will find different ones suggest different charging voltages, within the same general range as wet lead batteries. You need to check the manufacturer's specs for your batteries and compare them to your alternator/regulator. In the case of an Optima, it is designed to replace a wet lead battery and should work perfectly well on the same equipment, even if the optimum (no pun) voltages are slightly different.
With regard to AGM sucking the life out of an alternator...Bear in mind that depending on the overall capacity of your battery bank(s) and how deeply you discharge them, you can control that to some extent just by noting how much charge you need (i.e. 50% of 400AH? 75% of 800AH?) and not letting the demand go too far beyond what your alternator/regulator can accomodate.
Marine installations can kill alternators from heat, so good venting to the alternator, a blower if needed, or dual fans (at both ends) of the alternator can all help that.