To answer your first question, yes, you can monitor gauges while still using the stock tune after the accessport is installed to your vehicle. You can run the OTS cobb stage 1 on a stock car as others have said. Your factory tune will be saved in the "Stage 0" slot, so you always have the option to return to stock if needed. As far as the cobb OTS tunes go, skip them. Get a flash tune from stratified or other reputable tuner.
Just to clarify, Stage 0 is NOT the stock ECU that gets saved when you install the AP to the car. The ONLY way to go back to the stock tune is to uninstall the AP from the vehicle.
Stage 0 is a 'stock-like' tune. Meaning the throttle mappings, torque values, etc. are all the same as stock, but with the added COBB features (launch control etc.).
You need to install the AP to the car to get gauges, no way around that.
My buddy with a. FoST runs the COBB OTS 93 Stage 3 tune without any issues. Last time he had it on the dyno he put down higher numbers than everyone except an E30 Protuned FoST.