I have a self-employed version how do I remove the plus bundle for a free tax form?

If you are using the Self-Employed version then you are not using the FREE Version nor will you have the "PLUS" addition. 

If you did complete a return under TurboTax Free and added the "PLUS" there is no way to remove it. You will need to start your return from scratch. The "Plus" will allow your return to be saved for years so that when you come back to file your return next year you can carry forward your information into your 2020 return.

I filed last year but I don't recall being given the option of adding "Plus" and I can't find my 2018-2019 return.  Where do I find it?

If you used TurboTax Free and never took the "PLUS" it is very possible that you will not find your returns. 

To find your returns you will need to log in to your online account using the same credentials you used in the past to complete your returns.

https://turbotax.community.intuit.ca/community/navigating-turbotax/help/where-do-i-find-a-copy-of-my...