gps

GPS should work anywhere (at least outdoors).  Are you referring to Apple Maps or Google Maps?  They should both work.  I can't say whether you would have data (plan specific).  Make sure you have data roaming enabled.

On most modern plans your phone debería work in Canada just about the same as at home. There have been some recent complaints about data problems but not too many.

I've used in many times in the past (BC/Alberta/Ontario/Quebec) without issues.  Just ensure that data roaming is enabled.