Sounds like you've really been busy. I'm wondering why you decided to go with RO water? Is that what Macsdiscus keeps his discus in? I'm thinking chances are the discus you will get have not been raised in RO water. Unless your tap water is really way off in quality in order for fish to live well or you're considering buying wild discus, RO water is totally not necessary. Some people do switch over to RO when they want to breed because their tap/well water won't suffice. I have average municipal tap water, a little on the hard side, ph 7.4, dechlorinated for tank use with NovAqua+ and my discus thrive. They've spawned and I've had the eggs hatch without a hitch. I keep the tank at 84-86F. My tank is nicely planted low tech with minimal ferts and requires the least maintenance of all my tanks. If you get true malaysian driftwood, it will leach tannins very similarly to what wild discus live in in the South American Rivers. The wild discus habitat is mostly roots and some leaves, and basically devoid of plants, but dark from the tannins and soft. Bottled Black Water is absolutely not necessary to use to successfully keep discus. I boil driftwood before I add it to kill any bugs/bacteria, but not sure how you'd properly clean a 4' piece. Maybe soak in a clean tub with a little bleach added then rinsed with dechlor and left to sun dry completely. I always tell people be careful with sharp branches with discus. They are known to startle and dart wildly through the tank and sharp branches can do a lot of damage to a frightened, darting discus. No fish truly "like" bright lights, discus included. But they will get used to it. Most of the places you would get discus from do not keep them in brightly lit tanks. The lighting is more subdued. Discus can thrive in a big range of ph I'd say from 6.0 to 8.0. My tank stays at 7.6 and suits the discus and the other tankmates. I have rummies, cories, black neons, otos and a pleco. I have at times kept a clown pleco, common pleco, gold nugget pleco or bristlenose plecos in with the discus and have never had a pleco go for the slime coat. Your rubber lip should work out just fine. Otos will if they run out of food and get hungry. They are more of a true algae eater than plecos, so plecos usually go for any leftover discus food so they rarely are so hungry that they'd suck on slime coat. Out of the many varieties of tetras that I have kept in with the discus, I found cardinals and neons to not be very hardy. The rummynose are ok but mine basically stay away from the discus unless it's chow time. The black neons are my choice of neons for the tank for their hardiness, personalities and they do not fear the discus size as other tetras do. I think my rummies will live forever and netting them is impossible so until their numbers dwindle, I only have 3 black neons at the moment. I have standard hood lights with a 10,000K bulb for the plants and to show the nice colors of the discus. They are not super bright, but I did not think the yellow cast lights really show the true colors of the fish well enough. The lights in my tank are able to be on from 7:00 AM until 10:00 PM without algae issues of any kind. The cories I've tried over the years have included panda, false julii, albino aneus, and sterbai. The least shy and most active and amusing cories are by far the albino aneus. Mine never hide, always out in the front of the tank swimming and scavaging and they do fine in discus temps. The sterbai would be my second choice for a little smaller cory. I have a school of 19 in my planted 75G pleco tank and they are definitely much shyer than the albinos. False julies and pandas really don't do as well at those high temps, especially pandas. Get a nice size school of cories! I keep two 300W heaters in my tank. After a lengthy time of observing my 72G discus tank, I chose to take the AC 110 out and replace it with two biowheels because the AC 110 is just too much flow for the discus. They do not need or like that kind of flow. I keep both an AC 110 (on the right side of my tank) and a biowheel (on the left side of my tank) on my 55G planted sidthimunki, they and the cories love the flow. But having the AC 110 only on the right of the tank gives them a calmer area on the left side to retreat to. And I keep an AC110 on the left side of my 75G planted pleco (and others) and it blows the plants and fish at a very hefty pace! I'm surprised they don't get tired of swimming the current in that tank! But discus being so tall and flat get blown too much by the large AC. It doesn't matter what colors you choose, strains are color variations only, not personality variations. And the biggest thing is.....clean, clean water. Moreso for growing out juvies than for adults.
Good luck to you! Your will really enjoy keeping discus! They have a ton of personality!!