I repot my hempy buckets roughly when the foliage is just about the same size or bigger than the tub they are in.
Don’t listen to the ‘it has to go straight into the final pot’. Just get used to reporting abs watch a video on poo tube about how to do it carefully.
Iv never suffered any size loss from reporting and every time I report I have a load of pebbles stuck to the roots at the bottom that I have to remove.
Just be a bit careful and try not to rip the roots and your good. You should use some liquid kelp or kelp meal in your soil to help with root growth for this.
This is just my experience from having grown about 6 or so auto grows now.
Happy growing and try not to worry too much. Check out my critical orange punch diary. Granted that was a photoperiod, however, it took a hell of a punishment in veg.
It’s a shame you had problems in veg as with autos you have limited veg time.
Oh well, you will at least get some nice sticky buds, even if it is a small harvest, just try to compare your next grow to this one rather than comparing to the pro growers as that will make you depressed. You will get there instinctively for the most part though tbh