Multiple applications is a subjective topic. Ultimately, Google will assign our organisation a certain number of slots and we'll pick the student/project combinations we're most confident in. We can only choose
one application from any given person, and, if you have applied to other organisations then we'll need to talk to their project mentors about which one project you end up working on.
Submitting more than one application increases your odds statistically, however, we very much are looking for high quality applications over a high quantity of them, so it will also increase your work substantially. There's no clear winner in terms of the three projects you mention below (or any projects) because its really the details of how far you push the project and confident we are that you can deliver the project, that matters. By making everyone discuss on this list their ideas it will help you to identify who's working on what, and the level of quality behind the idea.
Cheers,
Sigurd.