I think you mean if you’re growing multiple strains how do you control how long to veg and when to transition.
If I’m right there’s not really a real formula for this. If you grow the same strain or one or two strains then it’s easy to keep a mom take clones and have a predictable flowering time to work with. Starting out that might be best.
I grow several strains at a time because I’m addicted to variety. I spend a lot of time researching my strains, ensuring they have similar characteristics that will allow them to grow together. If you have 4 foot plants and two foot plants you’re making things harder. If you have 7 week flower and 12 week flower gonna make it harder. I would keep plants off the same size and stature and similar flowering time.
I would spend the extra money for stable seeds. This will create less variation between plants and easier to maintain results. I’d stay away from crazy unpredictable polyhybrids unless you’re prepared to cull plants that don’t fit your mold.
Also keep consistent conditions. Don’t keep some plants in 2 gallon containers and some in 5 that will just create variation. More consistent the better.
Finally there will just be a learning curve. You’ll have to figure plants and strains out, learn how to read plants tell what they’ll do. With experience you’ll be able to tell what a plant will look like and make those selections with confidence. I have definitely had plants overgrow spaces and had to cut them in half, kill ‘em do all kinds of stuff figuring it out. Now I can run a small box with pretty much any stain and I always get my same 2oz per plant +/-. Best of luck as you live and learn 