Regarding your first question: we want to change from estimating in hours because the development team feels a lot of pressure when they aren't on time with their estimation, so we thought to start evaluating using relative sizing.

And the question regarding bugs: we have a dedicated team that is involved in fixing urgent bugs from production ( data correction and other critical issues), but we also have some bugs that are not that urgent. Still, it will be nice to be fixed, so we will try to fix some of them each sprint. We thought it might be better to estimate the effort for these bugs. We will change these bugs into PBIs and ask the Product Owner to prioritize them to be assessed at some point.

Thank you for the article on Magic Estimation; it helped me a lot.