100 Eevee

Vaporeon

Umbreon is totally useless. Espeon if you want to do solo machamp raid. Flareon is my favorite -> lots of damage. Vaporeon and jolteon isn't bad either.

has at least 2 100 iv eeveelutions, still asking for advice from mortals

Umbreon is not useless, it's really good against Alakazam and Espeon... that said, you just need 1 or 2 level 30 Umbreons, and you don't need good IVs for that, so evolve a high CP wild catch to Umbreon.

The 100... since you can't choose between Vap/Flareon/Jolt, I'd get another Espeon. Espeons are less replaceable in my mind than other eevolutions.

Which Eeveelution name tricks have you used?

Since you already have a 100% Espeon, I would just roll the dice on the Gen 1 Eeveelutions.