Will Christians be transfigured with the same glorious appearance Jesus had on the mount?
No. Scripture's use of “conformed”/“transfigured” shows believers are transformed and metamorphosed, totally changed from what they were before, but the context explicitly says we will not suddenly have the same kind of glorious appearance Jesus displayed on the Mount of Transfiguration. The change is real, inward and outward, yet not identical to His unveiled glory.
Les explains that the word “conformed” in Romans 12 is the same Greek word translated “transfigured” when Christ was transfigured on the Mount of Transfiguration. There He was changed before Peter, James, and John and took on all the appearances of His glory. Les says believers will not all of a sudden have that kind of glorious appearance as Jesus did, but the same root includes metamorphosis: we are to be metamorphosed, transformed, transfigured, and totally changed from what we were before, like a caterpillar emerging from a cocoon as a butterfly.
And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.