The sound post and bass bar in a fiddle are part of a lever system involving the bridge to translate side to side string vibration to vertical motion of the top (and to some extent bottom) of the fiddle. For it to work, the bridge has to be fairly tall - like on a fiddle. There have been some experiments on regular guitars using sound posts and bass bars without much success.
(But don't let any of that stop you from experimenting with it)
From my short building experience and research, a thinner top with some sort of bass bar or reinforcement will improve the tone(if nice tone is what you want!). Not having the carry through inside the box should also improve the tone(also more volume inside)-There is a builder out there that makes his with a carry through that goes behind the body. I'm not sure if he uses a bass bar and sound post- I have his plans around here somewhere.
Last thing -I started building an upright bass and was'nt happy with the low bridge. low bridge=low tension and volume.
A carry through is the neck going thru the box in one piece.(traditional cbg construction.) A bolt on neck would leave more air space inside the box.
I like that design so if u need to put a bridge post under bridge for bracing u can come off of that. Also on the bolt on design u can shim under bolts if u want your neck to angle down. That will help in string clearance. I dont know if this design is better than any but it's good to experiment.