Not sure what the other comment is referring to, but you’re right that PEX is much more flexible than PP. It’s commonly used in the US for residential plumbing, and is easier and quicker to install than PP, which is a big reason PP hasn’t replaced it (in the US).

Rechecked now, PEX became way more accessible it seems. Rehau-style toolkits used to cost several hundreds.

No, PEX is different. PEX is flexible, sometimes more convenient but requires more specialized and expensive tools to install properly.

You can install pex with just a crimping tool that runs around that price.