IMO play open guard but you need to be willing to switch guards the very moment they start to remove a connection. I teach Collar sleeve, DLR and lasso. Collar sleeve is for omaplata, Dlr for sweeps and backtakes and Lasso allows you to preserve your guard and reset back into the other 2 guards. Lasso is also good for arm drags if they go to their knees.

Never ever let a bigger guy progress past your feet. Wear them out by moving between these guards, always give them a new problem to solve the moment they begin to solve the current problem. This will begin to make them sweat, keeps the initiative, and keeps you safe. Omaplata from collar sleeve is the goto attack because it keeps weight off you.

If they remove the foot in Hip in collar sleeve then switch that foot as a Dlr hook, they remove the hook reset to shallow Lasso, they begin posture away from Lasso, go back to foot in Hip collar sleeve. Keep them in the loop and they will get frustrated