question

AH is just that Amp Hours so for series batteries the AH of one is the same as the AH of two.

Watt Hours is of course double because you have double the voltage. You have twice the capacity of one battery, with two in series but the AH rating, at any given discharge rate, is the same. It is probably worth checking that both figures are being quoted at the same C rating

AGM's are almost always sealed and vented... You do not want them venting under any circumstances because you cant replace the electrolite.

Most have recombiners to handle a small amount, a very small amount, of gassing during charging but you need to handle the cell voltage carefully and keep it below the gassing threshold.

The data sheet for the batteries will give you the absolute maximum cell voltage and current as well as recomended values that will give you optimal performance and life.

Generally the maximum current is fixed but the charge voltage is temperature dependent.

If you are not compensating for temperature, which you should be, you MUST, pic a value that is safe at the maximum temperature your pack will see when charging which will be above ambiant during bulk.

Also you will want a lower float that a typical wet cell... The datasheet is your friend, however this site is great for general info...

https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

I expect Victrol has it sorted with the switch selection but if it were me I would check against the manufactureres recomendations, 5 mins to check and adjust, years less service if you run over voltage.

AGM's are good but you only get one change to abuse them.

It is also worth pointing out that the makup of plates, and even electrolite in some cases, is an evolving thing so the latest AGM may not behave the same as an older one,

Sorry I cant comment on the actual charger, I simply dont know, but it is largely unimportent, whatever charger you were using the advice would be the same.

Hope that helps..

Al

2 6V batteries connected in series doubles your voltage to 12V but does not double your capacity.

2 12V batteries connected in parallel keeps your voltage at 12V but doubles your capacity.

Typically the 6V batteries have a higher capacity to begin with. So you have 225 aH instead of 80-110. You just need the double voltage so you put them in series and keep your 225.