For a hang on back overflow skimz makes a good one
https://www.bulkreefsupply.com/om5000-hob-overflow-box-skimz.html
or the CPR overflow
https://www.bulkreefsupply.com/deluxe-cs150-with-lid-and-aqua-lifter.html
Either way make sure to get an overflow with either two or three bulkhead drains so that you can set it up for Herbie style overflow or bean animal overflow. Both are great systems that make the overflow dead silent and utilizes an emergency drain so if your main drain clogs or experiences a backup the emergency drain is able to compensate.
Marine Depot did a great blog on all the drainage types give it a good read through
https://blog.marinedepot.com/education-center/charts-diagrams/durso-herbie-bean-animal-overflow
For a sump, were you looking for something pre-built or something you can make on your own?
If you're looking prebuilt i'd look at the trigger sumps if you're looking to do a refugium, in my opinion they are greatly designed for refugium use. I currently use the little brother of this sump the Crystal 30
https://www.bulkreefsupply.com/crystal-sump-36-trigger-systems.html
Return pump is really going to be up to you, there are AC pumps or DC pumps. I use the Sicce Syncra 3.0, but am looking to upgrade to the ecotech vectra S1 some day for more control-ability.