Who is the most well rounded heavyweight champion ever? Someone who is good or great in all of the following categories: Power, Hand Speed, Footspeed, Defense. Durability, Endurance, Ring Generalship, Killer Instinct. I'll probably pick Holmes or Ali here personally. Tyson is up there too except he was too temperamental at times.
To me, Ali checks the most boxes. Might not be the heaviest handed guy ever but all of the other characters that you mentioned, he has more than most.
First name that came to mind was Evander Holyfield. He could fight inside or midrange or even the outside.
Holmes and Lennox. Holmes was a great outside boxer who could duke it out on the inside when he had to. Had great footwork, great technique, decent power, heart, stamina, a solid chin and recovery abilities, and that dog in him that allowed him to win fights in tricky circumstances. Ditto for Lennox, though Lennox had a lot more power and was slightly less adept in the boxing department. Holmes as he aged became a canny dog who could beat younger men on experience. Lennox never really had a chance to prove that. Fury is pretty well rounded, but lacks a little in the power and durability stakes.
He was most well-rounded LHW ever, but like with Holyfield, who was the most well-rounder cruiserweight ever, he was too small. At HW... I don't know who. Probably Ali, Louis and Holmes. But none of them wa such well-rounded as Charles for LHW or Holyfield for HW division respectively