.like I was saying each circuit has to hat a separate neutral when pulling three twelves current carrying they need a separate neutral and when pulling over three current. carrying carrying conductors there's are factors to figure in so seven twelves that would be a neutral for each circuit which would be six plus a ground making seven being the max now in 3/4 emt right
3/4 EMT can handle sixteen 12AWG THHN/THWN conductors. How many of them are considered current carrying for ampacity adjustments will make a difference in whether or not they can all be on 20 amp overcurrent devices.
I think I know what you are trying to ask, but there is no straight answer. You need to figure out load(s) needed to supply, minimum conductor ampacity, ampacity adjustments, raceway fill for most every run you make. You do kind of see trends after you have been doing this long enough and can tell what is acceptable and what isn't often without doing any precise calculations, but still is no straight answer that always applies to what I think you are trying to ask.
I could run fifteen 12 AWG THHN/THWN in a 3/4 EMT plus 12 AWG equipment grounding conductor if supplying 5 three phase motors that only need a minimum branch circuit ampacity of 15 amps - because the adjustment factor @90C for 15 current carrying conductors puts 12 AWG at 15 amps. And the thing with motor circuits is the branch circuit overcurrent protective device may even be allowed to be up to 25 or 30 amps pretty easily on these circuits. You can't do that with general purpose 120 volt receptacle circuits though, you need to figure them as being able to handle full 15 or 20 amp depending on the overcurrent device. You could have sixteen 12 AWG conductors supplying nothing but 15 amp receptacle circuits though, and all 16 being current carrying conductors.