Total newbie power set up help

[Bugeye]

Hi new to the site ,wondering if you guys can give me some advice trying to sort out tge electrics on my day van for work , I will be running led lights ,diesel heater, laptop from 240v charger , programming equipment from a bench power supply also from 240v , maybe totally wrong but was thinking a split charge relay, 2x 100ah lesuire batteries ,1000w renolgy inverter. Main dilemma is the batteries, what type should I go for ? They will need to go in the back with me read you need agm because of fumes ? Absolutely no idea if this is true, second thing van has 14.4v from alternator so not ideal for agm anyway unless I go dc to dc charger , sorry the post isn't an actual motorhome but looking at the forum you guys know your stuff ! Thanks in advance