Below are photos of my bathroom DWV system on a bath I'm adding on to my house. The vertical vent lines run straight up a wall through the top plate where a straight 2" horizontal line links them up and connects them to a 3" roof stack. I'm in South Carolina which is an IPC state. Distance between toilet trap weir to vent is 6', tub trap weir to vent is 6', shower trap weir to vent is 5'. Toilet and drain lines are 3", shower, tub, sink and vent lines are 2". The toilet and shower/tub/sink drain lines sweep around ans join via a combo tee. After the combo tee the line continues on and joins the cast iron drain lane via Fernco's and a combo wye sweep. It's all solvent welded now. The project is at the framing and rough-in stage, so if anything needs to be changed now is the time to do it.
I await your comments (the "DMV" typo in the thread title notwithstanding LOL).