Hey Mark and welcome! Congrats on the big purchase, exciting stuff! Care to share what type of discus you ordered and what size and who from?
You should 10000000% add a pre-filter. It will make a world of a difference and makes filter maintenance much easier. Anything such as these from amazon will work... https://www.amazon.com/Leyouyou520-P...rfilter+intake
You could also make your own easily. Just make sure they get good water flow through them.
How much water do you plan to change and again, how big are the fish? I think those 2 questions will be the best way to answer your second question. I have always been a fan of a sponge filter. They aren't sexy, but can be hidden rather easy if you get crafty with some wood or plants. They are just the ol reliable of the hobby for me. So cheap, easy to use, clean and just a great filter alone or an amazing compliment. I say add one and hide it... I would grab a hydro iv or v and stash it in a corner. Always spend a bit more on a pump and get a nice quiet one. I have seen a few people post a cheap pump from amazon on here, the name escapes me but I am sure someone will chime in with it.
Sounds like you need to get your amazon cart fired up for those fish arrivals!