I think cross-court drop is not that effective in doubles.
Since you're dealing with a greater distance, it gives your opponent a lot of time to react. If you do a sloppy shot, they can perhaps brush the bird, net kill it or put themselves on the offense.
It's definitely effective at times. If you were deceptive and managed to sneak it in 1-2x a game, it may be effective during those times, but, don't expect it to be effective if it's your signature move from the very back corner.
The idea of a drive is to quickly react to any weak (flat) smashes or poor pushes. I guess it would depend, generally you want to drive back to the original smasher. He needs a bit of time to recover, especially if it's a jump smash. If he's cross court, then that could be a possible shot, it really depends on how strong your drive is. But keeping in mind again, if the shot is cross court, it gives your opponent a good amount of time to react and generally if you're playing against a good team, they can take advantage of that.
So again, it depends on the situation. If you can get away with the cross-court drives to take advantage of certain scenarios, then you should go for it. If you realize that they're mauling every cross-court shot you make, then it's time to adjust.
As for cross-court clear.. that is also pretty out there for interpretation. I mean, the pace for doubles is very fast. Generally, who ever is on the offense should be able to capitalize and end the rally, so you want to refrain from high lifts. I think that a straight clear in front of you would give you lots of time to recover and get into your defense stance. Also, depending on the situation, it could be a high clear, rather flat clear where the person in front can't intercept it, etc.
A cross-court clear in my opinion, would be need in really desperate situations or if you were lifting with reasoning i.e. exploiting their weakness. If you were on the left side of the court and you knew that the guy on the other team had bad footwork, then you might lift to his backhand and he may not be able to get there and be in a bad position to either smash and only able to make a poor drop.
What I'm trying to say is that, it's hard to generalize what is suitable and what's not, it really depends on who your opponents are and what you're capable of. This is called contigency thinking, to be able to adapt yourself to different environments.
