They can't possibly be root bound at this point. Just give them time to adjust to the transplant. Some plants get shocked more than others and take longer to recover and start growing
You will more than likely find you will want to lower the humidity as summer approaches, at least thats how it is on the east coast. Especially during flowering you want to maintain less than 40% to avoid mold.
Always pull the air, never push. Pulling creates a vacuum and the best way to test if you have achieved negative pressure is to put a lighter next to your intake and if the flame pulls towards the exhaust you should be good.
I have read more good than bad about Nirvana. The biggest thing is their northern lights are supposedly the best genetics and everyone that grows them has nothing but good things to say. Just because the seeds are affordable doesn't mean their are bad quality. They have been around a long time...
I would stay away from magnetic and try and buy a digital ballast that has the ability to dim your lighting. But out of the ones you posted I think the first one looks the best.