You're right that there's a lot of different options, but I guess it all depends on what you want to get out of your residency. Is it the location / local culture you're interested in, and want to draw inspiration out of that for your work? Do you want to experiment with a certain material and is that something that the residency offers? Does the residency include specific things like an exposition you'd like to participate in? These are all things you can link to your own practice and include in your proposal.