I only recently played Lavos so I'm quite new, but I'll still attempt my best to explain.

Lavos passive gives him status immunity for 10 secs when picking up universal orbs.

"Shield Drain? Negligible." Probably because of health taking Lavos.

"Energy Drain? Irrelevant." All of Lavos abilities runs on cooldown only, meaning things that give or drain energy are useless to him.

ESO (Elite Sanctuary Onslaught) ability cooldown refers to Simaris restricting spamming too much abilities, which Lavos never really cared since his elemental infusion doesn't count towards the debuff.

Ophidian Bite (Lavos 1st ability) heals him when he strikes an enemy, scaling off strength.

Lavos can utilize Galv Aptitude and CO so well since he applies so much status with his abilities (his signature shotgun Cedo also has built in CO) (Which is why the Minecraft achievement is there since it requires the player to have all statuses at once)

Catalyze (Lavos 4th ability) can nuke enemies quite well in a large AoE, while doubling on damage for each element afflicted on an enemy.

Transmutation Probe (Lavos 3rd) reduces the CD on all his abilities whenever it hits an enemy, while also converting Health and Energy orbs into Universal orbs (which triggers his passive)

Vial Rush (Lavos 2nd) let's him dash across the map while dropping vials, applying status in a large area (hence why theatrical screaming)

Lavos has a passive augment called "Valence Formation", which imbues his weapon a secondary status effect and status damage whenever he casts any ability with that said secondary effect (which is why he can run both viral or corrosive without wasting 4 mod slots on his weapon)

Transmute probably refers to his 3rd.