Mk7R or 7.5 R?
When the mk7 Golf was facelifted, VW’s marketing material said that the mk7.5 had new front wings, so if there are subtle differences in the area of the wing to bumper panel join, or if the headlamp units between the a mk7 and mk7.5 are a slightly different shape, a mk7 GTI or ED40 front bumper might not fit a mk7.5 R or a mk7.5 GTI bumper might not fit a mk7 R. The GTI and ED40 also have front fog lights whereas the R doesn’t, so I doubt the wiring will be there in the R for the fog lights to work.
Bear in mind that when the time comes to sell your R, swapping the R front bumper for one from a GTI might make some prospective buyers suspicious - they may think the car has had front end damage, hence the different bumper. You’d also need to inform your insurers as fitting a different bumper would be classed as a modification, and they may increase your premium.