Is it possible to link to a record and display in in a specific form (rather than the form saved on the record) without overwriting the form saved on the record? Basically I want to use a different form temporarily

You should be able to do this by tacking

&cf=[form internal id here]

on to the url. If you're redirecting into edit mode, however, that means that if the record is saved it will save that new form with the record, overwriting whatever form it used before (assuming you have the 'store form with record' option selected).

You can assign a specific form to a record for a role. Edit a role and in the permissions, assign that no matter what form was used to create it, display the record in a specific form.

I got it working using the combination of &cf described above, and then setting to the form I want on beforeSubmit in a user event script