The frunk is sealed, but the battery is not in the sealed portion.
Vented batteries should always have their vent lines properly attached. Sealed batteries don't vent gasses. Corrosion should never be an issue.
AGM is overkill for these cars unless you get a good deal. Lead acid is more than adequate.
This is my opinion. Do as you may.
I have a deep personal hatred for AGM. We tried for almost 2 years to work out assembly issues, going home every single day itching like hell from the fiberglass. When I left JCI, these issues were still a daily thing. Take that into account when you read my hatred filled biased posts about them.
