The American, who reached his first Grand Slam semi-final at the US Open in September, flexed the same muscles that have carried him into the top 20 in the world to reach his second title-decider of the season despite a poor second set.
"It was a weird match, but happy to get through," Tiafoe said. "In these kind of matches...it's not always gonna be pretty, it's not always gonna be your best stuff, but a win is what matters."
Kwon looked nervous at times in the opener and struggled to handle Tiafoe's deft mix of accuracy, touch and power as the American rattled off five games in a row before sealing the set 6-2.
Fourth-seeded Tiafoe upped the ante in the third, winning the two break points he needed to serve for the match at 5-2, only to stumble once more.
The American sealed the win at the second time of asking with a cross-court forehand.
Third-seeded Fritz downed Canada's Denis Shapovalov 6-3 6-7(5) 6-3 in the second semi-final.
They traded high-quality shots throughout the match as they split the first two sets.
Fritz slipped and still landed a brilliant lob shot to win the break point in the decider and go 5-3 up before sealing the match with an ace.
His victory ensured he will make his top 10 debut in next week's rankings.
It will be Fritz's third final this year, having won the other two at Indian Wells and Eastbourne.
