EHP Rollboard or, at less than half the price, the CeraTex product from Minseal.com in Tucson. It's exactly designed for engine compartment insulation. https://minseal.com/ceramic-fiber-paper/
It will do a lot for both heat and noise. The only challenge is attaching it in a curved space like a doghouse. It's super easy to use in lining a rectangular generator bay, but on a firewall or doghouse it takes some cutting and overlapping. You can use screws and fender washers to hold it in place.
Then, if you want more for sound, you can use the Lizard Skin on the inside.