Plumbing a Ready Reef tank for discus use, and other question ***LONG WINDED***

Greetings all, new to this forum and returning to Discus husbandry.
Some history of where I’m coming from in the hobby:
I started my 1st large tank (10g) in 1988, a planted display tank with 8 discus which grew to between 6”-8” and 2 breeding pair (some lucky person was given everything because they too had discus and I was moving to Portland, OR from Detroit area). Back then I could only get turquoise or 1 of the 3 wild species. No internet, limited readily available information, basically trial and error, but one of my degrees is in limnology (the study of lakes and streams ecosystems) and gave me a foot up. Needless to say all I did in general was 10-20% wc, fed quality food (raised small earth worms as one of their prime foods), and knew not to clean the aquarium meticulously cleaning, but did vacuum up food each day. That’s me, giving you an idea where I’m coming from (a born again newbie?).
Okay fast forward, I’m restarting and everything has gotten oh so complicated. What I’m starting with as my system:
I recently purchased a 100g glass reef ready aquarium (4 bottom drilled holes- 2x1” and 2x1.5”, top to bottom internal overflow weir, NO LEAKS), glass top, 1-Arctic T247 light, Aquaeon Proflex 1 sump, welded steel stand, drum roll please .....for $100 (I feel this is just short of grand theft). It came with really nice plumbing setup -4 grey flex lines,1 gate valve on main drain plus ball valve, all lines have at least a ball valve and multiple unions, except return).
Now my question I want to setup the overflow as a Bean Animal with return from center overflow splitting at a T to return water on both sides of overflow each with loc-line nozzle (which also came with setup)
1) What diameter should my main drain be (and why)
2) Run wet/dry, refugium, hydrid...what?
3) I’m thinking the sump is undersized, but, Aqueon says no problem, since it’s for freshwater not salt. What do you think and suggest if anything? (LxWxH of sump is 18.5”x9.5”x13.5” internal measurement (H) is up to top of pump chamber, and sock chamber (H) is 16 3/4”)
4) return pump size and choice? (I’m currently leaning towards a Current 6009 1050 GPH eFlux dc flow pump
5) heater size, suggestion? (Cobalt Neo-Therm 300 I always thought a good quality heater is one of most important pieces of equipment in a discus tank)
6) did I miss anything?
6) and FINALLY last question kind of weird and nothing to do with the actual build of the tank; Has anyone used a pair of food grade 55 gallon water drums as a grow out tank or juveniles. One to hold the fish (will have sponge filter and heater), the other to pretreat water (will have heater only), so as to do a 100% water change daily.
As title stated LONG winded... think of this as a community tank. Our community on this forum’s tank! I will try my best to follow consensus advice and purchases.
Thanks so much for taking a chunk of your day to read this and thanks for any advice in advance.
Eric

Hello Eric, here are my thoughts. For your main drain, I would use the 1.5” size. One for main and the second for your safety drain. You can use the 1” for your returns. The reason being your return will not out flow your drains unless you have a really high flow return pump. Also adding a gate valve to both return and drain lines allows you to make fine adjustments to balance the flow. As far as sump size it does seem small, going as big as will fit in the space will give you more volume and room to keep equipment clutter out of sight and add system volume for added stability. In my sump I’m using a filter sock tray first followed by 3 sections of 3” Poret foam then a open area containing a Purigen reactor and pump followed by 2 more sections of Poret foam. After that is a weir set at 1/2” below operating height which allows me to keep my heaters submerged at all times if I want to drain the sump for cleaning.The return pump is plumbed through a bulkhead in the end panel. Some folks like a glass tank for a sump but I prefer acrylic as it easy to drill where you want and glue brackets as needed for probes or other things down the line. As far as heaters go, I like multiples for backups and if you live in a cold climate you may need them. I use a controller to set temps rather than the heaters as they often fail sooner or later. Also as cheap insurance since they are sump mounted I don’t submerge them beyond the glass to minimizes seal failure. Return pump choice depends on height and distance and size of return plumbing to the display.
I went with an external pump, mostly due to my high head pressure from a basement sump, and previous good run of over 12 years on my saltwater reef tank. If there is anything you would like to ask feel free.