I'd suggest removable dividers in case you want to change things down the line or need more space. I'd also suggest removable bubble traps at the end of the sump before your return pump. That allows you to change your water level in your sump if you need unless you are using an ATO and keep a higher level. Even so, it's nice to have them.
I like filter socks and believe the more you have the better because you can go longer betwen sock changes and you go with a smaller micron sock and get more time on them.
I built in boxes that the water goes into before overflowing into the socks. It eliminates most of the microbubbles before they get into the main sump.
A lid over the sump is a great thing to reduce humidity under the tank and also reduce evaporation.
Here are a couple pictures of the boxes before the socks on my sump. The clear acrylic makes it hard to see. This is a picture while it was being made. It still has the paper on the acrylic and the sock shelf's were not built yet.
You can also see the lid which is 3 pieces. The back part of the sump lid is hinged. The front part is 2 pieces and has a cut out between the 2 around my skimmer.
You can see the sump lid in this picture and the hinges on the back half of the lid. It makes accessing the rear pair of socks and breeze under my tank which is 4' deep and those socks are situated at the furthest point.
Here is a shot looking down at the removable bubble traps in my sump. My sump flows directly into my fuge which is a second sump in itself. It also has removable bubble traps where the return pump pickup is. It also has a lid.
Another shot of the removable bubble traps and laser cut slots that also keep fish and other critters from going between the sump and fuge. (I have a bunch of live rock in that sump and a crab or 2)
The sump and fuge before I put it in. I did this as a retrofit from a wet dry filter. The tank was full of fish when I tore the old sump out, redid the underside of the tank and installed the new sump and new pluming. It took the better part of the day but the tank and it's inhabitants were fine.
Here is my sump design. Maybe you could get some ideas from it.