Joining Vegas with the preferred paths in the Stanley Cup chase were the Philadelphia Flyers, who got two first-period goals from Nicolas Aube-Kubel in beating Tampa Bay 4-1 to capture the top seed in the Eastern Conference playoffs.
Both winners completed an unbeaten run through seeding round play in the NHL COVID-19 quarantine bubbles, at Edmonton in the West and Toronto in the East, and became the teams to beat when the playoffs begin Tuesday.
Tuch beat Avalanche goaltender Philipp Grubauer high to the far right corner for his third goal in as many games with 16 seconds remaining in overtime to give Vegas the victory.
"I was shooting short side all game so I thought I would change it up a little bit," Tuch said.
Colorado's J.T. Compher equalized with 62 seconds remaining in regulation time to force the extra period, only to watch as Vegas advanced.
The Golden Knights booked a best-of-seven opening series against the 12th-seeded Blackhawks, who have won the Cup in three of the past 10 seasons. They upset Edmonton in qualifying.
"The Blackhawks have a lot of Stanley Cup experience, a lot of top players and a world-class goalkeeper in (Corey) Crawford," Tuch said. "So we've got to put a lot of pucks on the net."
Colorado will face 11th seed Arizona, which ousted Nashville in qualifying.
Philadelphia 21-year-old goaltender Carter Hart made 23 saves to send the Lightning to their first bubble loss.
"We played really hard," Hart said. "All the lines are rolling. All the D are rolling. We did a great job in there. We got in a lot of work. It's showing right now."
The Flyers, who were fourth in the East when the season was shut down, will open the playoffs against 12th seed Montreal, a shock qualifying winner over Pittsburgh after the Canadiens had the worst record of the 24 bubble teams.
Tampa Bay's first-round opponent will be the winner of Sunday's qualifying finale between Columbus and Toronto.
Sunday's other games will decide the third and fourth seeds, with Boston playing Washington in the East and Dallas facing defending champion St. Louis in the West.
The Washington-Boston winner will meet the New York Islanders in the first round of the East playoffs while the loser gets Carolina in the opening round.
In the West, the Dallas-St. Louis winner will open against Calgary while the loser meets Vancouver.