If you want to absolutely nerd out about running shoe foam, runrepeat did a fantastic writeup. I always hated that companies would give you a name for their foam, but they never actually tell you anything about what it means.
https://runrepeat.com/guides/running-shoe-foams-guide
Unfortunately altra ego p35 isn't on there yet, but it seems like it's polyolefin elastomer (POE) blend as opposed to the normal altra ego which is just EVA.
That's how I felt with the altra ego pro, which is TPE. I need to try the p35, though.