First, establishing “if the opponent has any two cards” is completely useless the vast majority of the times. You should always be given your opponent a range and then used THAT range as the calculation. Of course if your villain has a 80% VPIP then he is close to playing any two but that’s not the norm.

I’d say multiway pot calculations are extremely complex. They are difficult to figure out when you DO know the cards your opponents have, they are almost impossible when you don’t. Theoretically you could take their ranges, put them on pokerstove, check your equity against them given a particular flop and decide.

In practice I think there are way too many variables in this scenario to try to calculate odds of someone in particular having a draw and acting based on that, specially given there’re many other scenarios that are also likely and that you should consider (someone with a set does also have a “draw” to a full house, someone may have two pair and thus another “draw” to a full house). The term “draw” is usually applied (mostly) when it refers to a hand that goes from having almost no value to being a very strong hand if it hits.

On heads-up play this is quite important, on multiway pots this is less important as the equity of your hand will almost ALWAYS be less than the combined equity of your rivals. As that is always (or almost always) true, calculating the odds of someone having a draw is less important than evaluating if you hand is currently ahead of all the rest and whether your hand has the possibility of staying (or improving to) being the best hand.

There’s possibly other people here that may have better advice but in my case, on multiway pots (specially with more than 3 people including me), my concern is to figure out where I am, if I have a value hand and trying to narrow down their ranges. There’s only two ways gaining information in poker (other than cheating), betting or checking and observing everyone else reaction so based on my hand,  my odds, my positions and what others do I’ll decide my next action. I think on multiway pots on the flop it is a lot more about your hand, the board texture and the action than it is about trying to range other people. After all, with another 3 players each having a 20% calling range you have a mixture of really strange hands, specially since the range will get wider with each call (meaning UTG may have a 15% but button may be 30% and the BB can be playing any two)