Can for sure use Phylos testing to find the sex of fresh sprouts, if you can afford it, and you are limited in space it seems like a good option.
Can also test tissue for THC/CBD/Etc.., but I think you need a database of tests to compare it to. The amounts in a vegetative plant are so small, you need a lot of data to see an outlier, afaik. Nice tool for a big outfit to use, can help find better males before testing progeny, but a bit much for smaller operation. Also the tests are just data, they have value surely, but there are many things they do not test for, or do not understand. Some fantastic cuts, may test as average, while some of the outliers may only smoke average.
One thing to think about, is growing smaller populations over a larger amount of time versus a huge population in 1 round. As in, test 20 new females, 5 flower cycles in a row. Each time, including the keeper clones from the previous tests so they can grow side by side with the new populations, versus having 100 females to choose from all at the same time.
I just finished a round of 80 females in a 22'x24' room. Plenty of space, but still it is hard to select the winners, you can very easily make a hasty decision to later regret it.
Some traits stand out, and can be selected easily. Then you will get multiple plants that are very very similar, sharing the easy to spot traits, like bag appeal, calyx ratio, smell, flowering time. Although some of these twins, may smoke better, clone better, veg better. So you need to keep clones of each of them, and run them a second, third time, before you start to intimately know them. Out of 80 females, I narrowed it down to 19 keepers after 1 cycle. After processing, I noticed a couple I may have tossed that should have gotten a second chance. As well, I kept at least 5-10, that if they don't have stellar smoke reviews won't get a third chance.
The larger the population, the better odds of finding something special, and better odds of making a mistake or loosing something in the madness. So to me, to get the best of both worlds, multiple rounds of smaller populations. You get more time with each plant, and the stress and work load is lower.
I do some culling before flower, really depends on what you are after. You could cull runts, slow vegging, finicky plants if you are after something more commercial viable. Although if you are looking for the highest quality you may want to flower everything just in case.