I'm trying to sort out what I need to be aware of when swapping GCs to play with friends of a different nation. I want to swap to Limsa from Gridania. I am max rank in Grid. I'm currently PvP rank 20.

Upon talking to the Limsa transfer officer NPC, he only disclaims:
Please be warned: upon switching allegiance, you will be unable to equip items issued by your previous GC. Moreover, PvP rank, PvP EXP, and Action Points obtained as a member of your previous Grand Company will no longer be recognized. However, these PvP rewards will not be lost; they will be retained. Should you elect to reenlist in a GC, any previously obtained PvP rewards will be recognized once more. 15 days to switch again. 50k gil for another switch.
This seems to leave out the question of GC seals (which I thought were stored and not kept) and wolf marks. I just want to know what transfers, what resets, and what is laid dormant with the old GC. Thanks so much for any insight.