I really don’t know of a guide, maybe others here can help with that. I’ve been doing this for quite some time now and the comp setting is and always has been “What is the highest quality deliverable?” If you are going to be entering this in festivals, I imagine you will probably need a 1280 x 720 at a minimun.
As you stated before it easier to scale down than the converse. If you are worried about your computer and new one is out of the question, try pre-rendering finished elements and replacing them into your project. You mention green screen footage, instead of keying it, adding effects, compositing it over the background, just key it and render it out with an alpha and reimport as a new asset(though save your original keyed work compin case you need to go back).
Another stategy I’ve used when computer power is an issue is to render to a “PNG”(lossless) sequences. If for some reason the computer can’t make it through the entire sequence, I can just look at the last frame completed and start a new render from there. Then when I’m finished, I import the numbered “PNG” sequence, create a new comp and render that to my deliverable.
I’m sure some others can post some other stategies to get the most out of your computer. Good luck.
Johnny Cuevas, Editor
Thinkck.com