There has been lots of controversy about the 270 being good enough for elk but I don’t see a problem for deer. Maybe it has something to do with poor bullet selection but I know for my self, I’m looking forward to this season with my 270wsm. Either of the three you mentioned should work for deer without a problem.

As for optics I have a Nikon Gold and find it to be an excellent choice of scope. Very clear so the Monarch should be close in quality. I’ve never looked at the Burris scope so I can’t comment on them and the Browning and Weatherby rifles have never interested me. Good luck in your choice.