I avoid Steam and extra launchers due to performance issues. I only have 8 GB RAM on this small box. I recommend you keep your current Windows version and when the time comes, transfer it to the new SSD.
Currently I run Manjaro with XFCE desktop an Arch Linux based distro. Before this I ran Xubuntu which is part of the Debian family of distros. Manjaro out performed Xubuntu in my last testing. Even though you plan to use Debian please read this post.
I can’t speak for how easy it will be to install Debian with Wine. It will come with a software store you should be able to install Wine from there or you might have to drop to Terminal and enter;
$ sudo apt install wine
Either way, Wine is all you really need. Proton is what Steam renamed Wine. Proton is their proprietary version of Wine. So no one can download Proton and use it without using Steam. If Wine doesn’t work or has a low version number you might want to visit WineHQ to get the latest version. Manjaro has Wine at version 9.22 while WineHQ is offering 9.0 stable and 10.rc6 development. I recently have issues with alt+tab but I managed a simple workaround here.