Realistically you can't tell until the product is done. I have had plants that rocked out in veg and produced garbage bud, plants that grew like a sloth in veg and produced tiny little blueberry sized power house buds, and plants that were middle of the road in veg that EXPLODED in flower. ]
The qualities I look for in a mom are
1 veg growth ( Vitality / Vigor )
2 appetite ( how far can i push her feeding )
3 growth pattern ( I LST and train a lot so i need them to respond well to my efforts )
4 bud size
5 bud flavor
6 bud potency ( buzz )
7 Flower time ( 8 week

,14 + weeks

it better be the best of the best )
All of this being said it also has to out preform the genetics I already have available ( I already have a full plate at the moment of hand selected phenos )
Taking all of this in I would recommend taking cuttings / clones off each plant before you flower. then flower them all out, afterwards you will have another round that has been vegging while you flowered. This gives you a second round to flower out / mother plants to keep while knowing exactly what they produce.