can i remove iphotos after upgrading to photos?

You can but it is not a good idea - it will save very little space ( Photos saves disk space by sharing images with your iPhoto or Aperture libraries - Apple Support ) and can be difficult to restore if you want or need it in the future

LN

I think that is commonly referred to as burning your bridges behind you.

Exactly what do you hope to gain by delete iPhotos anyway?