still i need some guidance as too what would go where and how many inches to space things out.
Intake with skimmer (and filter sock) in the first compartment. the size of this will be dictated by your skimmer and filter sock. Make it just large enough for those.
This would be a good place for a heater as well.
I'm a fan of redundancy, so I would put one heater in the DT, and one in the sump. These would be slightly smaller than recommended, so together they do the job well, but if one fails, or get's stuck on, it won't cook or freeze everything before you figure it out.
The second compartment will be your refugium, which will be as large as possible.
The third compartment will be your return area. Like I said, if you use an ATO, this can be just big enough to fit your return pump.
A bubble trap is necessary before the return compartment. That would be a series of partitions, the first being attached to the bottom and sides, the second attached to the sides only and a bit off of the bottom, so water can travel under it.
The third is optional. This would attach to the bottom and sides as well.
I don't use a third partition on my sumps, because I believe air bubbles will float upward while water goes down under the second partition.
With just 2 partitions, and traveling through the refugium, you should not see any bubbles in the display.