Engine Roughness

Carb needle position can affect its running and changing needle clip position are affected by things like OAT, altitude, engine rpm, ect.. You'll  also find using gauges vs a  carbmate is far easier and you can diagnose with gauges, but is difficult with a carbmate.

For the average owner I'd  leave the needle clip in the #3 slot. If you think you want to move the clip you need to have a sound and good reason to do so.