As the title said, I customized my system according to what I liked. It's probably a mess of features and design elements cobbled together from the OS's I've used (or would like to use).
There's also some features I've customized that is hard to show via screenshots, like mouse gestures to move windows around different screens and virtual desktops.
I don't think I've achieved everything I want here, but it has gone way further than I've imagined it'd go.
How much time did it take? My experience with theming KDE Plasma was that it requires lots and lots of time and patience to achieve something good. At least for a newbie.
I've been working on it on and off since I've started using this system. It started with just the basics, tweaking the defaults, wanting more, and so on and so forth.
I usually can spend an entire (weekend's) afternoon just tweaking things, making a change here and then, and observing if I like the changes I've made. Rinse and repeat that over a period of several months.