FIrstly, a small disclaimer: this is not a proper guide, telling you which class should be best used and how to play them. For that, check out a far better guide here: https://steamoss.com/sharedfiles/filedetails/?id=3357848389

I simply like to dig out stuff from the games, and I like tables :) So I'm leaving that data below for all those folks who like to see the actual numbers for their heroes.
(Pity, that Steam formatting options are so abysmal.)

Characteristic
Used to detect whether enemy abilities would hit - Flying grants immunity to most Ground effects, Female is more resistant to Charm etc.

Succession Category
Each time you choose a new Emperor, game shuffles a potential candidates based on those categories (so you wouldn't get 4 Warriors). Additionally only Warrior, Coppelia and Last Emperor are considered 'strong' (used for operating Windmaker and in few other places throughout the game)

Tone
Describes whether class behaves as 'normal' or 'brash / wild' - it effects some minor dialogues in-game, mostly around Corsair quest.

Formation
Formation to be learned once you make that class your Emperor.

Resistances
Any inherent resistance bonuses. Only non-human classes have them.

Ability
Class-specific ability to be learned / mastered.

Glimm.
Glimmer affinity type, in other guides described as Spark Type. I have yet to dig out exact data from this version to check if it was changed, but for now I recommend excellent guide for the original / remaster: https://romancing-saga-2.blogspot.com/p/tech-sparking.html

INT
Hidden stat, in-game named Reason.

Ability:

Auto-Parry
Grants a 40% chance to parry attacks while equipped with a sword.

Models:

Ability:

Light as a Feather
Armor weight is treated as zero and no longer has an effect on speed.

Models:


Ability:

Swift Combatant
Grants a 30% chance to act first in any given turn.

Models:

Ability:

Ruiner
Increases the duration of inflicted status ailments and debuffs by 2 turn(s).

Models:


Ability:

Corruptor
Increases the chance to successfully inflict status ailments by 50%.

Models:

Ability:

Post-Combat BP Recovery
Recovers 3% of total BP upon emerging victorious from battle.

Models:


Ability:

Spell BP Reduction
Reduces the amount of BP needed to chant spells by 20%.

Models:

Ability:

Max HP+
Increases maximum HP by 10%.

Models:


Ability:

Max BP+
Increases maximum BP by 10%.

Models:

Ability:

Resplendence
Recovers 5% of total BP when delivering a successful basic attack.

Models:


Ability:

Auto-BP Recovery
Recovers 2% of total BP when it is the character's turn to act.

Models:

Ability:

Critical Striker
Grants a 20% chance to ignore enemy defense when attacking to deliver critical damage.

Models:


Ability:

Tough Hide
Grants a 20% chance to completely nullify an attack dealt to the character.

Models:

Ability:

Spell Damage+
Increases the amount of damage dealt by spells by 10%.

Models:

Ability:

BP Saver
Decreases the amount of BP consumed by techs by 20%.

Models:

Ability:

Provoker
Increases the chance of being targeted by enemy attacks when using counterattack techniques.

Models:

Ability:

Vigorous Attacker
Increases damage dealt by 10% when the character is at full HP.

Models:

Ability:

First Striker
Allows the character to act first on the starting turn of each combat.

Models:

Ability:

Waste Not, Want Not
Grants a 70% chance to prevent consumable items from being depleted upon use.

Models:


Ability:

Chemist
Increases the amount of HP recovered when using consumables in battle by 200%.

Models:

Ability:

Damage Converter
Increases the Overdrive gauge by 5% whenever the unit suffers an attack.

Models:


Ability:

Healing Potency+
Increases the amount of HP recovered by spells by 20%.

Models:

Ability:

Auto-HP Recovery
Recovers 20% of total HP when it is the character's turn to act.

Models:

Ability:

Overdrive Gauge+
Increases the amount of Overdrive gauge gained upon attacking by 50%.

Models:

Ability:

Survivor
Leaves the character at 1 HP when suffering large amounts of damage, provided they had at least 30% HP remaining.

Models:

Ability:

Tech Damage+
Increases the amount of damage dealt by techs by 10%.

Models:

Ability:

Cutpurse
Grants a 15% chance to steal items from enemies when delivering a successful melee attack.

Models:


Ability:

Scavenger
Occasionally loots 2x more of certain items upon emerging victorious from battle.

Models:

Ability:

Pyro Benison
Completely nullifies all damage dealt by pyrology spells and heals on fire leylines. Also includes synthesized spells. Beneficial effects are not ignored.

Models:

Ability:

Terro Benison
Completely nullifies all damage dealt by terrology spells and heals on earth leylines. Also includes synthesized spells. Beneficial effects are not ignored.

Models:

Ability:

Hydro Benison
Completely nullifies all damage dealt by hydrology spells and heals on water leylines. Also includes synthesized spells. Beneficial effects are not ignored.

Models:

Ability:

Aero Benison
Completely nullifies all damage dealt by aerology spells and heals on wind leylines. Also includes synthesized spells. Beneficial effects are not ignored.

Models:

Ability:

Analysis
Increases the amount of damage dealt when striking an enemy's weakness by 15%.

Models:

Ability:

Umbral Benison
Completely nullifies all damage dealt by umbrology spells and heals on dark leylines. Also includes synthesized spells. Beneficial effects are not ignored.

Models:

Ability:

Penny Pincher
Recovers 25% of the Overdrive gauge upon successful execution of a United Attack.

Models:

Ability:

Smithy
Increases weapon attack and armor defense by 10%.

Models:

There is only one Automaton in-game: Copellia

Ability:

Poker Face
Grants a 20% chance to completely nullify an attack dealt to the character.

Ability (Gerard):

All Attributes +1
Increases all basic attributes by 1.

Ability (Last Emperor) :

Ability +1
Increases the number of available ability slots by 1.