She can only summon one Carbuncle or Fairy at a time, and only if she's using the related job - Summoner for Carbies and Scholar for Fairies. She *can* swap them out, but it's a long cast and she usually doesn't bother (unless it's between fights/rounds, that is). I do not intend to break this particular limit, since it forces a certain amount of tactical awareness.
The chocobo is always out - it's like your average warhorse, basically.
The history viewing is based on the memories of the person she's interacting with, with very few exceptions, and it's never total knowledge - it typically just grants some insight on the current situation from the source's point of view. For a recent example, she was able to view the Warriors of Darkness taking on a primal and thus discover that they too were immune to tempering (mind control). The longest-reaching thing that's happened in canon thus far is witnessing the true beginnings of the Ishgard-Dragonkin war, through the memories of Hraesvelgr (one of the eldest dragons). It doesn't give her two-way telepathy, but it does make her able to receive. And it gives her an almost total resistance to mind control (I've yet to hear or see anything to suggest it isn't actually total, but wanna leave the remote possibility open for potential game shenanigans).
As a side note, the Echo's history viewing aspect is not all that common - it's used very sparingly in the game, and will more than likely be a mod/player consent required thing.
As for the other job classes: Most of these just amount to the ability to use a given weapon, at her level. Black Mage is a notable exception, in that it gives her access to different combat spells than she has as a Summoner (namely fire, ice, and lightning). Weapons she is proficient with include: Tomes (summoner and scholar), daggers (rogue), one-handed sword and shield (gladiator), staves, wands and rods (conjurer and black mage), greatswords and firearms (basic proficiency only, dark knight and machinist respectively), bows (archer), fist loads/empty hands (pugilist), and axes (marauder). If you guys want, I'm fully willing to drop everything there except summoner, scholar, and maybe black mage - she's definitely not one for up close and personal combat, anyway.
Re: Questions!
The chocobo is always out - it's like your average warhorse, basically.
The history viewing is based on the memories of the person she's interacting with, with very few exceptions, and it's never total knowledge - it typically just grants some insight on the current situation from the source's point of view. For a recent example, she was able to view the Warriors of Darkness taking on a primal and thus discover that they too were immune to tempering (mind control). The longest-reaching thing that's happened in canon thus far is witnessing the true beginnings of the Ishgard-Dragonkin war, through the memories of Hraesvelgr (one of the eldest dragons). It doesn't give her two-way telepathy, but it does make her able to receive. And it gives her an almost total resistance to mind control (I've yet to hear or see anything to suggest it isn't actually total, but wanna leave the remote possibility open for potential game shenanigans).
As a side note, the Echo's history viewing aspect is not all that common - it's used very sparingly in the game, and will more than likely be a mod/player consent required thing.
As for the other job classes: Most of these just amount to the ability to use a given weapon, at her level. Black Mage is a notable exception, in that it gives her access to different combat spells than she has as a Summoner (namely fire, ice, and lightning). Weapons she is proficient with include: Tomes (summoner and scholar), daggers (rogue), one-handed sword and shield (gladiator), staves, wands and rods (conjurer and black mage), greatswords and firearms (basic proficiency only, dark knight and machinist respectively), bows (archer), fist loads/empty hands (pugilist), and axes (marauder). If you guys want, I'm fully willing to drop everything there except summoner, scholar, and maybe black mage - she's definitely not one for up close and personal combat, anyway.
ETA: Forgot to mention lances, as a Dragoon.