Big upsets are unlikely as a human coach (too bad you’re not a sim) but there are things you can do to try to disrupt their gameplan. That is essentially your goal.
Slowdown, -5, double the shooter(s) is the common upset special. You can do that. Most high seeds will be well prepared to withstand that most nights, but bad sims happen to all of us, and if you get the juice that night, it can be glorious for you. But again, most high seeds have more than a couple shooters (they don’t have to be 3pt shooters to blast a -5) so that heavy negative is more often than not just increasing their margin of victory. But on the other hand, you’re rolling the dice for an upset, not trying to decrease the final spread. That’s why this one is very popular.
If you press, you can’t double specific players, but you can move guys around to line them up against their most effective scorers, and I do that in a pinch. You don’t control where the help comes from, but we can assume the listed SF is at least involved in defending the 3 area most of the time. The “lockdown” concept is clearly not as strong as it is in man, but it’s not nothing. Moving guys around also makes you less predictable, and as a disruptor, that’s good.
Another approach - I’m much less worried about modulating distribution than some of the other opinions you’ll get, especially in this instance. You are the disruptor. It is not in your interest to be predictable. If your opponent game plans, it is likely they will just look at 3-pt tendency, some efficiencies, and move on. They are unlikely to double anyone (as that can backfire and increase team efficiency) so choose a spot to attack and put your most efficient guy (hopefully a 3 point shooter) there. Maybe go up to half the distribution on the floor (I normally don’t go over 33% for any one player, and very rarely reach above 40%) if you have one dependable scorer. Roll the dice with him having a good night.
Ultimately, to beat a clearly better team, they will need to draw the “sucks to be you” card, because at this spread, you can seriously outcoach them, but you’re only looking at decreasing that margin by 10-12 points most nights, against most of those caliber teams. Regardless, you want to approach these things from a disrupting standpoint, think about the things you can do that might take them away from what they’re trying to do.