How do you determine which drop pod goes where?

If manually kicked out of a platform, I think it just goes to whatever is free. Though it seems like if a cargo landing pad is requesting it seems to go to that one specifically.

I was hoping to block drops of certain items to certain pads, but that doesn't seem possible. Even if a pad is specifically requesting a maximum of 0 items, it'll still get the items then immediately trash them.

probably best bet is to make a general purpose one and place that first, and connect a shitton of cargo extensions to increase its "reception capacity"
Also, doing things by request rather than manual drop is probably ideal/better, as then the platform above will only drop what is needed and to the landing pad that needs it.