Roof vent and leisure battery

[falcoron]

Can someone who has done this recommend a roof skylight with built in fan for my 2011 transit hi roof? There is a ribbed roof so what’s best one to fit over these ribs and seal well?

Also was looking at leisure batteries and was initially going to put in 2 100ah lead acid but then thought a 180-200ah AGM types would be fetter and take up less room. I have a victron smart 30amp charger I used without issue on my boat
Are these a good choice any caveats?
Cheers