Thank-you for your input @jakefowler I appreciate that you must have 1000's of customers and you can't cater to everyone's personal whims!
Personally I like to just have the model on my primary screen, and drag the browser off onto my second screen. So for example in Inventor I will also drag my toolbar off in a vertical layout onto my second screen.
Fusion has brilliant keyboard shortcuts, right-click menus and the S key menu. So I very seldom break my concentration on the model by having to move the mouse up into the toolbar anyway.
I also have an extra 7 buttons on my mouse that are mapped for enter, esc, etc. So I don't have to jump around all the time between the keyboard and the mouse.
I also have a numpad for my left hand so that my mouse hand can stay put 😀.
In terms of foreground, middle ground and background. My opinion is that at the moment the toolbars style puts it in the foreground, where I would prefer a slightly lower contrast, making it more middle ground. There is a photo editing program called Raw Therapee that I personally love the UI of. The toolbars are quite muted, but light up when you mouse over them.
And while I am muttering on here, I also enjoy programs that have scaleable toolbars. Especially as screen DPIs get higher.
Fusion has been so well configured for top-down modelling and has such a smooth feel. I feel this really complements the mindset I am in when problem-solving and designing. And I personally feel that my points above would enhance the feel/UX even more.