Wine attempts to translate Windows calls into Linux, its developed by Codeweavers whose focus is/was application compatibility.
Valve took Wine and modify it to best support games, the result is called Proton. For example:
Someone built a library to convert DirectX 9-11 calls and turn them into Vulkan ones, it was written in C++ and is called DxVK.
Wine has strict rules on only C code and their directx library handles odd behaviour from old CAD applications.
Valve doesn't care about that, they care that the Wine DirectX library is slow and buggy and DxVK isn't. So they pull out Wines and use DxVK.
There are lots of smaller changes, these are 'Proton Fixes', sometimes Proton Fixes are passed on to Wine. Sometimes they can't but discussion happens and a Wine fix is developed.
The splash screen (boot screen instead of text)used to get me. It provided by an application called 'Plymouth'.
You used to need to install it and configure grub, however I think if you go into 'System Settings' and type 'Splash' KDE has an option to install and choose the screen