Dual batteries with Redarc charging questions

Hey everyone, I'm deciding on a dual battery setup for my truck and I'm pretty set on the split battery setup under the hood, and am thinking of using a Redarc BCDB 1225D to charge the Aux battery. My question is what are the most optimal batteries to use in this scenario? Dual AGM is what I've seen from some people, but from what I understand the Aux battery will be the only one that takes a charge directly from the Redarc, leaving the starting AGM to whatever the alternator puts out. Which I imagine this could cause the starting battery to fail over time by the drop in voltage (unless running an additional volt booster). I've also considered just using a regular Lead Acid for starting and having AGM for the aux battery to keep the batteries in the best health. Either way the AGM batteries I'm looking at are the, X2Power Group 35 from Batteries + Bulbs.

Appreciate all the help!

 

Run dual AGM. You'll be fine unless your alternator craps out and then it doesn't matter what batteries you have. I've run dual yellow tops for years and no issues.