I have one, and had a kyleena for years before that (not recommended for endo, just for birth control). Insertion and removal can be pretty rough, but for me it was nowhere near as bad as a bad pain episode.

I like mine. I get no periods. So less pain. No fun getting the IUD put in or taken out, and I still know when I should be getting a period based on discomfort and hormones. It didn't stop Endo from coming back, but it's better for me than no IUD.

I am new to Mirena, I had my put in 2 months ago. My understanding is that experiences vary a lot, but here is mine. I found the process of having the Mirena put in very uncomfortable and the period cramps afterwards were very strong - hopefully you won't feel the same but I recommend clearing the following day, just in case. I have experienced spotting and very light periods since, but I'm confident it is causing the bleeding to reduce so helping on that side of things.
I also experienced quite a lot of aching around my cervix for the first few weeks. I am told it is common for it to take 3 to 6 months to settle, so I'm hoping to see further improvement.