Maybe I'm over thinking it and it could be simpler but this will be the first sump I've ever made and I'd like to do it perfectly

I'm five years out of the hobby after relocating but I've been getting the itch recently!
I moved from Ireland to Poland, and while my salary decreased, unfortunately the price of setting up a tank did not. However, it's very exciting for me to think about how to do as much as possible by myself. I plan to only buy fish, salt and test kits from a fish shop, everything else I want to make/source myself.
I plan on setting up a tank around 30g simply because I want to be able to do everything myself without getting help with any heavy lifting etc. I used to have a 75g with fish and a few corals running on 2 canister filters and a skimmer, but now I just want something low maintenance with 2 clowns and cleaner shrimp and maybe one more fish.
The bio load will be quite low so I think this sump should suffice.
My main questions are, would a small plenum even be worth it? Same with the dsb? and how big of a return pump will I need.
Any opinions will be greatly appreciated.
Thanks
