I don't know about nerfs, but these buffs would be what I want for my characters:
Lao :
Spin moves forward to make sure F1 xx Spin always connects, maybe even B32 which would be great. Not needed tho. F1 spin working without meter is needed imo.
Orbiting hat +16 on hit, make it easier to F1, can F4 for more damage with same link as now. Also F1xxSpin would always connect, hopefully, with aforementioned change.
F2(1) whiff issues fixed
Don't think 21212 needs to be mid at all, it's pretty much relegated to a punisher for me. F21 doesn't need to be safe either since he has F1 string.
Johnny:
F344 never whiffing on Erron and maybe other characters (only certain it works for erron)
d1 jails into St.2 on hit on everyone, not just males. All that needs to be done is extend the hitbox lower.
Forceballs can be consistent but I don't think it's absolutely needed.
Good god give him a throw KB you monsters wtf.
F4 could be faster but not needed.
Fix his KB requirements somehow. Either make it so parry always does, or make it easier somehow. As of now he's basically not an entire character. KB's completely useless.
Fix F4xxCamera flash and F344 camera flash, or whatever. I don't use that variation but it's probably the worst in the game. Probably gotta fix the shades too but I don't know enough about it.
Maybeee buff recovery on Brass Knuckle buff.
I think both of these characters are very good characters, with tons of potential held back by some slight inconsistencies and/or bugs/shitty variations.
Only nerf I can actually think of for a character I use, would be Sub Zero's F4, on Flawless make it -7. I think he'd be fine. Maybe make F2 unsafe on block as well so he can't stagger it and must commit if he throws that out.