I have both bar ends and an aero bar on my flat handle bar road bike... plus I cut an inch off both ends of the bar. Everything will fit, you just need to move stuff around to where it's comfortable for you.

Trick for getting grips to move if you have or know someone with an air compressor. Blow air between the bar and the grip and it will move around on a cushion of air.

The bar ends that mount on the inside of the handle bar didn't last long. To get enough holding power to handle the torque applied to the bar ends the mechanism either had to be extremely long and beefy (i.e. heavy) or it would distort your handle bars making it next to impossible to ever change components on your bars.

Most bike shops will mount the bar ends for you at minimal to no cost assuming they were purchased from them.