Hi! I interviewed at Ottawa twice in a row. First time, I was good waitlisted but never made it off and was lucky enough to get in this year! To answer your questions: no my application generally remained the same but I worked on incorporating a lot more CanMeds in my ABS (my activities themselves didn't change much). My wGPA did go up thanks to my fourth year marks (although this likely did not have a significant impact on the interview invite and rather helped me after the interview stage). I think you have a good chance of securing an interview the year after provided your Casper performance doesn't change as mentioned above! My biggest challenge was the interview itself - I prepped a lot more the second time around and it definitely helps having experienced it once before.
Let me know if you have any other specific questions or PM and I'm happy to help