Your starting power forwards in 2018.
Celtics - Horford
Nets - RHJ
Knicks - Zinger
Sixers - Saric
Raptors - Ibaka
Bulls - Markannen
Cavs - Green
Pistons - Griffin/Harris/Tolliver
Pacers - Young
Bucks - Giannis
Hawks - Illyasova/Collins
Hornets - Williams
Heat - Johnson
Magic - Gordon
Wizards - Morris
Warriors - Green
Clippers - Griffin/Harris
Lakers - Randle
Suns - Chriss/Bender
Kings - Randolph
Mavs - Dirk
Rockets - Anderson
Grizzles - Green
Pelicans - Davis
Spurs - Aldridge
Nuggets - Milsap
Wolves - Gibson
Thunder - Anthony/Grant
Blazers - Aminu
Jazz - Favors
Of those, only Zinger, Griffin, Giannis, Randle, Randolph, Davis, Aldridge, Milsap, Gibson, and Favors are players that Tatum cannot handle defensively one-on-one. Everyone else is either in his same weight class or not skilled enough to take advantage of Tatum.
Of the ones I just listed, only Zinger, Griffin, Giannis, Davis, Aldridge, and Milsap have the ability to turn the game based on that matchup.
In other words, Tatum can win the matchup with at least 2/3rds of the league at PF. The Cs would have to gameplan for the other 1/3, including doubling the post and playing big with Baynes.
The whole "power forward" thing is more in the mind.