Walker is half an inch taller, nearly 3 inches longer, about 10 pounds heavier (probably about 25 heavier than Murray) and significantly more athletic than White. Physically, he's essentially a longer Simmons.
Of course he's not equipped to defend overpowering big wings/combo forwards, but there's plenty of "SG"'s they're likely going to have trouble defending. He's the most natural defender for the likes of Harden, Thompson (though they might prefer him on Durant), McCollum, Booker, Mitc , Oladipo, Beal, etc.