To answer your questions: yes I have grown with H PS, my first 12 years was done with two 400s. Yes you are best to start all of the seeds of one kind, then pick the best one and clone that one from then on and drop to rest. Then repeat the process for the other strain. Yes it's true you waste a lot of water with a reverse Osmosis system. My water bill went up from $18 before all the way to $20 now ;-)
For the feeding, all of my veg plants are sharing a reservoir so they all get the same feed. All of my bloom plants are also sharing one reservoir so they get the same feed, except the amnesia haze needs to go a little longer. While the main reservoir is flushing at nine weeks, from then on the amnesia haze will get a custom mixture suited to its 13 to 14 week booom. It will be separated and the nutrients delivered in a standalone DWC while remaining in place in the same cabinet .
However, unless the amnesia haze is amazing I will be dropping it. It was a gift from a friend, so I am going to try it out a couple times, but will kill it if it's not really special as the extra time and complication of an extra solution is annoying. My other strains all finish at about 10 weeks and share nutrients.
Let me know if you have any other questions, or if that is clear?