If I were you, I would grow out more than one or two of those new seeds. If you only grow one or two, you may not end up with the "cup winning" pheno. You want the best possible chance of getting the best pheno in the pack. A 10 pack is a very small run to find the sought after pheno depending on how much work was put into the strain, how stable it is, etc.
I have only grown hydro once, and it was DWC. Everything worked out great for me. Since then, I have just used soil. I usually don't start to reduce my nutes until I start to flush. A lot of people will tell you to start to lower the nute dose, but I never had, and I haven't had any problems. I may have to flush a little longer, but if the plants are using the nutes I giving them, I figure why the hell not.
If they were all clones from the SAME MOTHER, they should all finish fairly close to each other. If they were different sizes going into flower, they will be different sizes finishing flower. But as long as they were from the same mother, they will finish close. If they were clones from a bunch of different mothers, they may finish at different times just like seeds would.
The shorter ones will have less bud sites because they are smaller. The shorter plants may even have smaller buds, mainly because they are further from the light than the tall ones. If the short ones were closer, they would probably have the same size buds. If they are farther away, as I'm guessing they are, put them on top of a box or something to get them just as close as the tall plants.
With only 250watts, you don't want your plants much taller than about 12"-18" when they finish, and I stick closer to 12". The 250watt light can't penetrate that far. If plants are too tall, it causes the plant to use its energy on the lower buds that will never develop. And this inhibits the energy to the buds that are getting the light.