There is no right answer.
However, I think I can clarify what you've read so far. You need a buoyancy engine to supply the thrust, wings to direct that thrust, and some ability to change your pitch angle when you change the buoyancy. So, you'll need to balance the strength of your engine with the drag created by your wings. At the same time, your wings need to be big enough to convert vertical forces of buoyancy into horizontal motion. (Generally, the shallower depths you work with, the less power your buoyancy engine will require.)
This is a complex problem, and the existing solutions to it vary wildly.
The Seaglider AUV (built at the University of Washington, now owned by iRobot) is shaped to achieve laminar flow. The antenna attaches at the back, allowing the vehicle to communicate while pointing nose-down at the surface. It has no external moving parts; all control is done by shifting weight internally.
The Spray Glider (built at Scripps Institute of Oceanography, now owned by Bluefin) is a more cylindrical shape. The antenna is located in one of the wings, and the vehicle lays on its side on the surface to communicate.
Slocum gliders go for a cylindrical shape that's more suited to the pressure housing. They have an electric powered version, but the real magic is in their more modern "thermal glider" -- they take advantage of the fact that pressure increases with depth but temperature decreases with depth to make an engine that requires no (or very little) electrical input. Like Seaglider, the antenna is in the tail.
The Liberdade XRAY is shaped like a flying wing and (to my knowledge) is actually the fastest autonomous underwater glider ever made. It's more for naval use than scientific use -- it tracks submarines.
Approaching the problem (from scratch)
If you can't find a hydrodynamics expert to help (which would be the best option), I would suggest starting with your buoyancy engine and working outward.
- Figure out how much buoyancy your engine can create
- Figure out how much power your engine requires
- Decide how large of a battery you'll need -- this will be a significant proportion of total weight
- Explore your ability to trim your vehicle (likely by moving the battery fore and aft) and calculate the pitch angles you'll be able to produce
- Repeat steps 1-4 as necessary
- Make a prototype shape, make its buoyancy half of what the engine can produce (minus a little for safety). Then drag it to the bottom of a pool and see what happens.
- Repeat steps 1-6 as necessary