Can respondents re-open and edit a response?

I'm interested in your product to create a conference RSVP form.  Some of our attendees will need to submit once to confirm that they are coming and reserve hotel rooms, but then edit the form at a later date when they have flight details.  Will they be able to do that with JotForm, or will they have to submit a new reservation that we'll have to reconcile with the first submission?

Yes, this is possible. Please check this guide to know how: https://www.jotform.com/help/40-How-to-Let-Users-Update-Their-Form-Submissions-at-a-Later-Date.