Window snapping was implemented some time ago: https://www.macrumors.com/2024/06/12/macos-sequoia-window-ti...
Instead of win key, you can press F3, or just set a hotkey that works for you in the System Preferences
Instead of clicking the red maximize button, you can double-click the window header / title. This will use an algorithm to try to resize the window to the best size for its content.
full screen is still its own thing as you mention, though