I'll add my 2 cents since I just went through this.
Back story: had 2 paralleled 12v flooded lead acid batteries that final died (got a long time out of them which was cool). Not ready to go lithium route so went with two AGMs. Dropping batts in was plug and play, but make sure your battery comes with the manufacturer's recommendations of bulk, absorption and float voltages.
Things I did with that changeover:
1) Solar: tweaks to my solar controller to match my bulk, absorption and float to the specs of the battery.
2) Shore power: kept my Intellipower with charge wizard, but only use that in the field when bulk charging off my Honda EU1000i generator. I do NOT leave this powered up anymore when the van is just plugged in at home, I only use it for short term bulk charging if the solar hasn't been able to keep up out in the field. I added a simple remote control outlet so I can have the van plugged in but not have the Intellipower powered up (
https://www.amazon.com/gp/product/B07W53C4FQ). That works nicely if I'm somewhere plugged in and want to be able to use coffee pot or space heater but don't want the Intellipower running day after day and trying to equalize.
3) Added Battery Tender trickle charger that has AGM setting (also controlled by remote control outlet), for when the van is at home and plugged in, to keep the batteries nice and topped off and in their happy resting voltage (so at home when not using the van, trickle charger on Intellipower off). Used this 4AMP model (
https://www.amazon.com/gp/product/B07XMJDJX7) in case I'm out somewhere plugged in and don't want the Intellipower on but want to keep up with a few LED lights etc. 48w is more than adequate unless I'm running the furnace all night.
4) Biggest change is I installed a DC-DC charger. This involved running new 6GA (because the old 8GA was looking suspect and was mildly undersized for the length and wattage) from the original battery separator to the batteries under the gaucho. The plus here is that on long drives I'm not just trying to stuff 14+ volts into those batteries for hours and hours, the DC-DC charger (I standardized on all Victron stuff) will take power from the alternator and treat it just like a solar controller does, bulk charging then going to absorption then to float (with the float value being user configurable so I set to to what the manufacturer recommended float is, 13.2-13.4).
Between the DC-DC charger and only using the Intellipower for bulk charging on rare occassions I'm hopeful I've removed the two most likely overcharging sources and hope for some long life from the AGMs.
-- Bass
just helped me with an upgrade to inverter/charger system. This is a wiring diagram I made, and ran by the guys at SMB. 
Linear Mode
