All three of those players are out for the season, so the Habs and Knights won't face any major cap issues this season, but the remaining teams, including the Leafs, could be forced to play shorthanded at times and may even be forced to subtract a player via trade to remain compliant with the salary cap.
With LTIR, teams try to get as close as possible to the cap before placing players on it, to allow for maximum cap flexibility. This season, 4 teams were able to come within a few dollars of the cap limit. Courtesy of CapFriendly, 5 teams were within $175 of the cap - Vancouver ($0), Toronto ($4), Vegas ($16), Tampa Bay ($33) and Edmonton ($167). Of those five, only Tampa and Toronto have current rosters of 20 players instead of the usual 22 or 23.
Thanks to the almost flat cap again this season, one third of the entire league will be playing "cap gymnastics" all season to stay compliant and that could mean we see a few key players being offloaded for draft picks or prospects.