Greetings!
If you really want insulation, I would suggest that you get the best for sound deadening. None of it works good enough for temperature control to make it worth the cost or effort, and in many instances the negatives far outweigh any positives.
If you focus on sound deadening, it can make an especially huge difference while driving. It’s also important to cover all interior metal surfaces to create a thermal break between the outside skin and the interior. It takes very little exposed metal to have a large negative effect. Most people use automotive carpet, perhaps trunk carpet, which is similar to felt.
It should be mentioned that only active heating & cooling can keep you comfortable year round. Both can be cheap, easy, and extremely energy efficient. I can expand on that if needed.
Cheers!