I think his handle is better than 95% of the league. Maybe more. Most of his turnovers are not due to a bad handle but due to bad decision making. Make better decisions, which lead to so many less turnovers and everyone would rave about his handle. I actually think he has a better handle than Tatum. Tatum makes better decisions.
Absolutely not. 0.95 x 450 = 427.5. Let's say top 25 handle in the league.
I can quite easily list more 40 players with a better handle than Brown.
Trae, DeJounte Murray, Kyrie, Marcus Smart, Brogdon, Tatum, Simmons, Rozier, Ball x 2, Garland, Doncic, Jamal Murray, Dinwiddie, Lavine, DeRozan, Kevin Durant, Curry, Cunningham, Poole, Haliburton, McConnell, Morant, Wall, Lowry, Reggie Jackson, Oladipo, LeBron, Jimmy Butler, Paul George, Brunson, CJ McCollum, Lillard, Jrue Holiday, D'Angelo Russell, Devonte Graham, SGA, Chris Paul, Devin Booker, Donovan Mitchell, James Harden, Tyrese Maxey, De'Aaron Fox, FVV, and Mike Conley.
That is about 45, just from a cursory glance at starting calibre ball-handlers. I could probably go on.