You're talking no-gi I assume? In general I do anything I can to get on top. This is not the time to work my fancy subs from the bottom. I'm getting older and I can't afford the potential injuries. Me on top = me safer.
If they're on their knees I'd say butterfly guard is a great game to play. You can manage distance, and mix in your hook sweeps with seated wrestling, arm drags, 1 on 1s, base out and snag the front headlock, etc. If they stand or post on a foot or hand from a hook sweep, it's great to transition to your X guard or 1 leg X guard. From there you have such a strong manipulation of their base that they should be pretty easy to sweep.
If they're on their feet instead of their knees, you can try to enter directly into your X or 1 leg X. You could try to come onto a single leg from the seated guard.
The spiral/reverse delariva is also a great option. The free leg is great for managing distance so they can't smash you. The primary attack from there involves inverting and rolling through to the back. I have mixed feelings on this against bigger guys. it works great if your technique is sharp, because if you do it properly their weight should not be on you as you invert and spin under. But if you haven't put in the practice yet you could find yourself getting stacked badly. I still think the spiral guard is great for tripod sweeps, coming up to singles, arm drags, kimura sweeps, overhead sweeps, or going to the reverse x guard.
Closed guard is also a good option for slowing things down if they get out of hand. I'm not a big closed guard guy in no-gi, but it's solid. I'm mainly not big on half guard against big strong dudes because of how easily they can smash you and you lose your ability to control the distance. I would give an exception to the "waiter" style deep half or even the Jeff Glover style deep half where you use your outside or inside foot as a hook. Regular half I hate against big guys. Even lockdown. it's great control, but I'm also pinning my own hips in place and I think it's too energy intensive compared to some easier ways to play guard and sweep.
Watch Marcelo Garcia and Rafa Mendes.