1. get the compensated model if a. you don't care about the flame being a target indicator in low light or darkness, b. you figure your night vision is gone anyhow when you pull the trigger; and c. you haven't been taught a shooting technique that minimizes recoil.
Oh yes, I have compensated barrels on some guns - then again I had the barrels compensatied before I understood the drawbacks stated in the first paragraph.
Any further modification is optional.
2. I do get the 3.5 pound connector. My mentor prefers the 5 pound.
3. I do put on iron sights. I blew off the factory sites once and I know another guy who did. The Glocks shoot fine without sights, but people will be commenting on your situation. Try this experiment and you will understand. Put electrician's tape over the front and rear sights one time at the range.
4. I have Robbie Robar do grip reductions. Don't do it unless you try someone's Glock who has a grip reduction. If you don't need it, spend the money on spare lifetime parts and factory ammo.
5. I finally broke down and put on extended mag releases on the older Glocks. I didn't need to do so. However, if Glock went to the concept, I figured that there must be a reason.