Steam runs natively. It is a linux application (to my knowledge, and it wraps "a webview", so there might be some nuance here. But native enough for this distinction).
Steam uses a compatibility layer called Proton to run Windows games under Linux. Running the games that way is not significantly worse. It can get the same or even better performance (but sure, sometimes worse) and will affect battery life pretty much exactly as if running the game via Windows on the Laptop.
Proton is based on Wine, and Wine is not an emulator. Translating the calls does not make them heavier.
Functionality for older windows games is a little bit more absurd. I have a few games I kinda gave up on because they stopped working on windows 10, until I chucked them into proton or wine and suddenly those games were working. That was a confusing evening for a moment.
Steam uses a compatibility layer called Proton to run Windows games under Linux. Running the games that way is not significantly worse. It can get the same or even better performance (but sure, sometimes worse) and will affect battery life pretty much exactly as if running the game via Windows on the Laptop.
Proton is based on Wine, and Wine is not an emulator. Translating the calls does not make them heavier.