Re: theoretically, how do you reduce variance at the cost of value?
If you want to reduce variance, the typical method is "when you are not sure whether to call or fold, fold". If the decision is very close then the EV is close to 0, and the variance of calling will be larger. The earlier you fold, the better, so basically you can start by playing tighter.
If your bluffs are very low earners (including meta-game) then you can consider reducing bluffing considerably also. Whether or not this is feasible depends on how tough your competition is (so does the folding method, of course, because observant opponents will bluff you more)