Mixed AGM & Lithium charging -specific questions

[Toys_with_time]

Have been reading a lot about mixing batteries and because my 2 x alternators are internally controlled, and I have 2 new starter LA batteries but completely dead 690Ah AGM house batteries, was thinking about buying 340 or 510Ah of Lithium and using either 2 x 60Amp DC : DC with integrated MPPT solar chargers (Renogy) or 2 x 120 amp Sterling Pro DC : DC and existing separate MPPT to charge the Lithium, with the alternator in both cases remaining connected to the start batteries.

3 questions:
1. If I have 2 x DC : DC chargers hooked into the same Lithium bank will they play nicely if both engines are running or solar is coming from both of them (have 2 solar banks)?
2. Since the Volvos have MDI black boxes is there any easy way of getting a 12v trigger feed for the DC : DC charger when an engine is running?
3. I came across mention of the Mastervolt Charge-Mate Pro 90 today and was wondering if that was an alternative to a DC : DC charger given it can output 90 Amps which is closer to my alternator output? Says it can handle Lithium but doesn't say if it can handle both at same time and not sure how it differs from a DC : DC charger and again whether 2 of them will play nicely?

As always I look forward with interest to the forums response(s).

TwT

ps interesting that the site changes DCC into an emoji if you don't add a space