On my old Aqua Medic skimmer it had a little box on the end filled with Bio-Balls, worked well for removing Micro-Bubbles but required cleaning every so often, not the easiest task, I'd use vinegar to soak them in, then air compressor to blow them clean.
In the sump I've seen the three piece design that seemed to work well, you make dividers two are the same height & the middle one is lower than the other two, creating a bubble trap. The middle is actually attached to the bottom, the other two are left off the bottom usually an inch or two.
Now when it comes to actual plumbing you can use several methods, hoses are easy to install and you will have less restrictions due to the hoses being curved and no sharp turns great for some application, but it does come with problems that hard PVC overcomes, mainly once you hard PVC glue piping your done with it, personally I prefer the hard PVC and just up-size the pump a little to overcome the head loss due to the 90's &45's & other head losses. PVC takes more planning & design up-front but in the long run IMO once done you can focus on other things & lessen you chances of having flow problems later down the line.
