Sorry hit post before I was able to write anything.
designing my sump for either 125 or 120.
Can I get some constructive criticism on both designs.
I personally like the first design the best, and plan to use the refugium for plant cuttings, and possibly some additional bio media. I had a saltwater sump for a while, and really liked having a whole extra eco system. So thought about adding sand, and planting the cuttings from main tank, add some shrimp and snails.
You already have had sumps before so you know a lot about what to expect when dealing with them. I will say if you have small fish and shrimp in the sump you can expect them to 100% go over that baffle unless there is some kind of screen in place to stop them.
The baffles and all the extra media/mechanical filtration are also overkill so you will be making more work for yourself then necessary but otherwise won't hurt anything.
I personally wouldn't want a permanent planted tank in my sump because it just adds to the maintenance in dealing with that system, but lots of folks create a space for temporary plant survival until they can give away/sell plant cuttings.
The more baffles you add will allow more co2 to escape. I had something similar to the first design without the last two baffles at the end. If I had to do it again, I would make the distance between baffles wider to make it easier to clean - at least a hand wide. The other thing to consider is placement in the cabinet. In my case the door pillar made it awkward to reach in and clean in some spots just because how things lined up.