Camper charging setup options (Inverter, Voltage step up, cigarrette socket, DC-DC)

Bluetti AC200MAX in a 2011 Mercedes Sprinter 2.1L 4cyl

Goal: To achieve a high charge rate while driving the van in a safe manner.

Current plan: Run a 700w inverter by Kickass from the starter battery (This specific inverter allows me to adjust the voltage parameters for it to automatical turn off when the car stops running. CONFUSED as to why inverters don’t have the option for a D+ signal shut of, I guess they are not normally setup to run only when the cars running). Plug the T400 that came with the AC200MAX into the DC input. Locate this Inverter plug in an accessible location to use for shore charging when available. Then run solar to the aviation connection as per usual to provide a constant charge when the sun is shining. The following is a diagram of the setup.

The following images are pathways I went down a rabbit hole to confirm my plan is the most efficient, cost effective and SAFE option. There were so many variables and scattered information it was hard to work out for a solid amount of hours researching.
Voltage step up setup

This is the Voltage step up setup created by Scott-Benson his post is under fast-car-charging
I really admired this test and the attempts from others gave me courage to research into it with the 20amp version and a fan to keep it cool, some people worried me attempting this without even understanding the importance of thick gauge wires. (FIRE HAZARD). This is what mostly turned me off the idea. The voltage step up converter I eventually found pretty cheap here at $139 is tempting. But the 100w extra isnt enough for me to purchase this under reviewed product, and its quality of build is questionable, plus the overheating aspect lead me to choose the inverter option I showed previously even knowing its less efficient its still designed only to be a bluetti charger.

The next option was just a cheaper option and simple setup but pffft who wants simple and less wattage!!
cigarrete socket setup

The next setup I put way to much thought into and realised the inverter option is way cheaper. This option might be more efficient in the way I am not doing DC-AC-DC but I am using the solar charge on the DC Enhancer which is limited and not cost effective… and also much more expensive.
DC-DC setup

NOW I am going to explain why I went away from the first option… Stupidity… I really wanted this to be automated I didn’t want to have to use a high current switch in the car every time I turned it on and off. My van has a smart alternator so a VSR wouldn’t work I attempted some research into 40amp 5pin high current relay with a low current signal switch, this worked but faulted out the smaller inverter I already have and I had to reset it once the car was running and it ran fine (Believe it is the voltage drop or peak that freaked out the inverter while the battery acts as a buffer, I am not 100% sure, I might test this with the new 700w inverter).

What is everyone’s thoughts? Open to opinions and people like me who do too much research before they do anything hahaha. Hope this helps someone looking for options.

If the voltage parameters don’t work, I might test this new 700w inverter with a Stinger 200 Amp Dual Battery Isolator / Relay / I am not sure if this will work? Designed to isolate another battery and close the circuit when the cars running, will this work?

something like this but the switch will be an ignition signal