The grips use a standard bar end plug as do lots of other grips. The metal bit at the end of the grips clamps around the end of the bar to secure the grip. Not quite sure how bar end mirrors fit BUT the hole at the end of the bar is available for use when using these by removing the end plug, no need to cut hole.

The type that mounts on the side of your handle bar with a clamping mechanism inside the tube - yes. Others, which wrap around the outside of the tube - no.
Better to look over your shoulder anyway :-)

Yes no real drama.

The grips are tubular with no sealed end so there is no need to cut them, just slide everything further in for bar-ends or whatever...

Yes, I have fitted end bars - no problems.

The end of the grip is open, and they are supplied with a plug to fill the end of the handlebar. So if you leave the plug out it should be easy to fit the mirror to the bars.

Yes, they have an open end on them - although they would look kinda weird.

you could move the grips further on your bar then fit the bar ends. I would however suggest buying the grip with the integrate bar as this will be more of a suitable position and width for riding.

Yea as they are open at both end's with an end cap to blank the hole

No problem, I have a pair fitted outside my GP1s.

Yes, I have fitted end bars - no problems

They are shorter.

For me better palm grip and that means less fatigue on my hands and forarms.
This means more comfort and longer rides.

The right grip is shorter to facilitate the fitting of the grip shift mechanism without forcing the right brake lever too far away from the normal hand position.

The length is the same - 132mm - it's the size of the palm area that is different.

I have the Large Gripshift version, and it is 95mm long overall

Thats a good question and one i didn't think about when i bought them. But, i'm pleased to tell you that they will fit both standard 25.4 and oversize 31.8 bars as the width at the grip end of the bars is identical.

I have the large Gripshift set, fitted perfectly to a handlebar with an outer diameter of about 22.28mm (I believe that's about 9/10ths of an inch).
The grip has an aluminium collar which tightens around the bar, so inner diameter isn't important.

Yes. I fitted end bars with these - no problems

it comes in a pair pack