As for removal, you can usually peel them (with patience) after the glue is heated. That could be either a heat gun or a few hours under the sun. The glue remnants on the window I was able to clean with isopropyl alcohol.
The windows I had to deal with were the barn door ones with the defroster. The once grayish tint film was already transparent from decades under the sun and the scratch protection paint over the metallic lines of the defroster didn't held up and came out with the film despite me being very careful. At least it seems that the film removed only the scratch protection paint and none of the metallic lines.
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As for the new tint, I think in 2021 I had one installed on the wife's car, and it had a ceramic thingo added to it that really made a difference in temperature control. It was a bit more expensive, though.