First, yes, I think Reggie Miller would thrive today. And to address another poster's comment, yes, I think Larry Bird would have been great in any era. The whole extent of my thoughts on this topic have included that the best players in any era would be very good in any other era as well. It is players further down the roster that are so much better today.
To address the other point, however, you could not be more wrong. The game today is far more mobile than our golden era comparison. It is not even close. There is some good data available on the number of miles run during games that shows this.
But, one of the most definitive takes on this I've seen is from Steve Kerr, who unquestionably has a lot of credibility on the topic. In a nutshell, he is skeptical he would play today, despite his elite shooting ability, due to his belief he would not be able to defend in today's league. It is extremely difficult to defend today for a variety of factors, but what looks like bad defense is actually incredible offense and the difficult positions it puts individual and team defenses in.