Paracelsus I removed the top feed from my small box and I agree with you: it's fairly useless to me. When they're small, until those roots start reaching the reservoir, I give them shots of water as needed. The top feed in my big box goes on twice a day for 5 minutes. Though I'm not really sure it works all the time...
I give a 24-hour flush as needed, if I see signs of nute lockout. Haven't had to so far on this grow, but I think I will give them a flush on Saturday and then add nutes on Sunday, because it's true what they say: plants love a little breather from the nutes. But I'm pretty conservative with nutes and never reach Advanced Nutes' recommended doses.
I can drain the reservoir in my big box by putting the pump into the drip feed mode and opening up a valve connected to a hose going into a bucket. I use a small wet vac with 2HP for the small box. I hold the roots back with one hand so they don't get sucked up. I change my water and nutes every Saturday, religiously.
The small box has 200 watt CFL bulb in it, and it does a great job. The big box uses 400 watt MH and HPS bulbs. (I took a portion of a small inheritance and invested in solar panels a year ago, and got 55% of the cost back from govt.)
I also had to invest in a chiller for each box:
https://www.amazon.com/Active-Aqua-...=1514380198&sr=8-1&keywords=reservoir+chiller
Before I installed the chillers, root problems were chronic. Now the water stays at 68-69 degrees. For my environment, that was a necessary investment: it can get very hot in the summer. I keep the AC at 74 degrees and feel less guilty cuz of the solar panels. I have a 50-pint dehumidifier for flowering.
So consider how hot it will get in the summer months, and if you have a cooler place to grow rather than, for example, an upstairs room. But you've probably already thought of these things. Root rot is the scariest thing about DWC, and it can be horrifying.
How big will your reservoirs be, and how many are you going to have? You said you have a secret room for your grow: hope it's cool!!!