Small boat lithium battery system

[LaughingGull]

Hi all,
Wondering if I could get some feedback. My boat, Laughing Gull, is a 32' sailboat. I plan on doing some extended cruising and so I want to upgrade to lithium.
I currently have two group 27 AGM dual purpose batteries wired with a 1,2,Both switch. The existing alternator is an internally regulated 55amp Hatachi mounted on a 3GM30F. The system I have works well enough for my existing power needs, but now I am adding refrigeration to the system.

My questions are:

1. When using a DC to DC charger, should there be a lead battery in line between the alternator and lithium battery? Or can a DC-DC charger be wired directly to a lithium battery without the need of a lead battery? I am considering installing two Dakota 135 dual purpose batteries that will in effect replace my AGMs and at the same time provide more than double the power.

2. Is an alternator upgrade in my future? The main source of charging will be the alternator. I want the ability to charge the batteries as quickly as possible without excessively compromising the engine, thus I am looking for a "best fit" alternator. Maybe the alternator I have now will do the job but where it is internally regulated, I just don't know.

3. Lastly, does anyone have experience with the use of two DC to DC chargers in an effort to get the most out of your alternator and decrease the time needed to run the engine to charge batteries? I see that Victron offers a 12v 30amp charger. If I install two of these in parallel does this mean a 60amp alternator will keep up? And just to help me understand, if I installed three of these chargers will a 100amp alternator keep up?

There's a lot to unpack here.
Thanks for your help in advance.

[SV_Wanderer]

One option you might consider is to replace the starting battery with a lithium one; Dakota is who we went with as well, replacing 4 6V golf cart batteries with six 135ah Dakotas for the house bank, and one more for the starting. They make a number of options (including these) that can serve as starting batteries (and have BMS designed for doing so). That would let you sidestep the DC-DC charging issue.

However, I suspect you’ll need to switch to an external regulator at the very least. We have a larger alternator (120amp) on a Beta 25, and needed a Balmar regulator, brush box, and cooling fan.