SLAYER. I did not use splines for the top plate.
I use splines to define the complex shape first. Although you can create a perfect Cage if you like.
However: I do use box method and splines when I model. It depends on what I’m trying to achieve.
The circular protrusions for the buttons were very easy to create.
I use DISK tool to create the 8 sider. Then I use stencil tool to project DISK on to the poly surface. Last step is to weld the points to the 8 Sider.
I generally like to use 8 sider for the Sub-d circles, the reason as it creates more evenly precise circle. Any way, this is how I like to do it. And it works for me.
Pleas keep in mined that there are many many ways to model. Most people in time do develop there own styles and techniques, just because it works for me may not work for you.
Good Luck and have fun