If planned and done properly, IPRs are okay to gain space to move or retract teeth.

I would personally limit IPRs to front teeth only as it is very difficult to do a good IPR on posterior teeth.

It would depend on your treatment plan and needs whether IPR or extraction is more suitable for you.

if you feel your teeth is very protruded and needing lots of space to retract inwards, then extraction would be a better option for you.

if its only minor changes probably only go with IPR

Usually there is a limit how much IPR we can do. also dependant on your tooth size or enamel thickness. some people have bigger or wider tooth means probably having a thicker enamel so more room to shave.

Generally shaving is no more than 0.5mm on each side. but during the shaving procedure, if you start feeling sensitive, do let your dentist know.