"That's where the game is going, with mobile defensemen," Golden Knights general manager George McPhee said.
Brannstrom describes himself as an offensive defenseman who thrives on the power play, but acknowledged he has little patience for those who question whether he's big enough to play in the NHL.
"I am undersized and I can't do anything about it," said Brannstrom, who weighs 173 pounds. "So I just try to play my game and be smart. There are much smaller 'D's in the NHL."
Brannstrom models his game after countryman Erik Karlsson of the Ottawa Senators, even though Karlsson is 2 inches taller. However, there are smaller defensemen who have thrived in the NHL, including Ryan Ellis (5-10, 180) of the Nashville Predators.
"I try to work a lot on angles," said Brannstrom, who added, "maybe in a couple years" he'll be ready for the NHL.
Brannstrom impressed during Vegas development camp and is playing for Sweden in the 2017 World Junior Summer Showcase, with games beginning in Plymouth, Michigan, on Saturday.
Brannstrom and fellow first-round picks centers Cody Glass (No. 6) and Nick Suzuki (No.13) each signed a three-year, entry-level contract with the Golden Knights on July 15.