Just to clarify, when we're saying "top16/top8" we're referring to the amount of players, right? Not the amount of matches?
If we are talking about top 16 players, then that would mean there are 8 matches total, 4 in winners and 4 in losers to start.
From here, the total amount of winners matches up to before grand finals is 7 matches, and the amount of losers matches up to before grand finals is 14, for a total of 21 plus grand finals which would be 22, or 23 if there is a bracket reset.
All of top 16
22-23 matches of 1-set per match of 3/5 games (8-9 winners, 14 losers)
Top 16 to Top 8 only
12 matches of 1-set per match of 3/5 games (4 winners, 8 losers)
All of Top 8
10-11 matches of 1-set per match of 3/5 games (4-5 winners, 6 losers)
So, if we are splitting top 16 and top 8, you're basically dividing the number of matches in half, but splitting winners and losers of all of top 16 would have more games on the losers stream. The losers stream can also easily get held up by the winners stream, so I don't think that's a good idea.
Math time!
The SG timer is 3 minutes which is 180 seconds.
For argument's sake, let me define the worst and best case scenarios:
Worst case scenario is every game going to time-up and all 5 games being played, including bracket reset.
Best case scenario (realistically) would be half the timer (90 seconds) and every game being 3-0, including bracket reset.
Per set
Worst case: 180 x 5 = 900 seconds per set, or 15 minutes per set
Best case*: 90 x 3 = 270 seconds per set or 4.5 minutes per set
for all of top 16
Worst: 900 * 23 = 20,700 seconds = 345 minutes = 5.75 hours
Best*: 270 * 23 = 6,210 seconds = 103.5 minutes = 1.725 hours
Skullgirls' Tournament Mode cuts down between-match time so drastically that the numbers above are actually pretty close to how the tournament would run in their given scenarios. Other fighting games tend to go on longer due to button checks, round transitions, and needing to repick your character/team every game, on top of any game-specific attribute such as the actual speed of the game or any kind of mechanic that freezes the timer, of which SG's is extremely minimal.
I'm not sure how practical it is to run all of SG top 16 in a single 2-hour block, when considering the grand scheme of things for a tournament of this size, but I think it's definitely possible.