For pearls, I've read that the known SMG, assuming more then 1 of each type, is a Tediore that bounces around liked a Rubberized grenade and fires everywhere like a Bouncing Betty, and that the bullets reflect off surfaces. Or something along those lines.
I have also read that the known Sniper is always Shock, and seems to have a large cover-ignoring AoE on it, comparable to a launcher or even a Norfleet/single Norfleet ball.
For the buffed Seraph stuff, IIRC it is everything that was from Scarlett and Torgue DLCs.
Spell card! Diamond Will ~ Unbreakable Determination!
Bearcat - Dahl AR Effect: Fires 3 grenades that ricochet and explode dealing massive damage. Think Veruc + Grenadier.
Avenger - Tediore SMG Effect: Reloads have a Bouncing Betty effect, ammo regen a la BL1's Tediore legendaries.
Butcher - Hyperion Shotgun Effect: Enhanced fire rate and magazine size, reduced projectile count, shots fired have a chance to add ammo into the magazine instead of consuming it (same effect as 5 Shots or 6 Gunzerker skill).
Sawbar - Bandit AR Effect: Guaranteed fire elemental, no other effects confirmed.
Storm - Maliwan Sniper Effect: Shots generate explosions like the Pimpernel, guaranteed shock elemental.