Something that makes quite a big difference to sync'ing is whether it's an effect that is triggered by the note (ie. a delay) or something that is constantly running. If it's triggered by each note played, you can get away with nearly having it in time because it doesn't have much opportunity to go out. I think there are some clever modulation fx that re-trigger with new notes but most sequence-y stuff doesn't, so you either need to play to a click or relegate it to studio use.
Something that makes quite a big difference to sync'ing is whether it's an effect that is triggered by the note (ie. a delay) or something that is constantly running. If it's triggered by each note played, you can get away with nearly having it in time because it doesn't have much opportunity to go out. I think there are some clever modulation fx that re-trigger with new notes but most sequence-y stuff doesn't, so you either need to play to a click or relegate it to studio use.