It does vary depending on the variety but the ideal root mass will depend mostly on the pot size. That will result in a given ideal stalk size for that amount of soil.
If you veg too long and the root mass is too large for the pot it will dry out too fast and be very hungry. If you pot up and switch to flowering before the root mass is established you will end up with a waterlogged, overferted, poor yielding plant with leafy harsh fluffy buds and a small stalk. It may also take longer to finish or never seem to finish.
For 4 gallons of soil in a 5 gallon pot, ideally stalks end up about the size of a dime. It is in the outdoor systems that I have seen the wrist sized stalks. Results may vary in different types of systems but I am referring to organic soil systems.