(W)INE (I)s (N)ot an (E)mulator. It's not a virtual environment either. It's just a compatibility layer that wires up calls to Windows libraries to their Linux counterparts. Proton is an enhanced fork of WINE.
Sleep mode is just... sleep mode, and consumes 10% of your battery per day.
DosBox runs on Windows, too.
The Steam Deck is a weak ass PC. I love mine, but it does not compare to a modest gaming PC.
I haven't gamed on Windows since buying my Deck, but you're testimonial here isn't very convincing. It's a portable gaming device that requires a dock (or hub) to even play on a monitor. It's underpowered by design. Not even all top Steam games run on it.