I agree with Rustyspoon#

I like the toolbar floating my self

Look at My DAW setup
[Linked Image from i.imgur.com]
If you look closely at it, you will see many floating things show when I move the main screen between monitors 2 & 3 (Top and Bottom), my transport stays where I want it.
We should give users a lot of freedom to set things up as he likes.
A few things should stay where they are set, like the "File icons" and the Main controls on the left.

Here is a image showing some guide lines

[Linked Image from i.imgur.com]

Starting with your
General foundation:

YES (should be 3 "lite/med dark/Dark" and at the same time, good contrast) Dark mode (BB is killing my eyes)
Yes (See Image) Design around core functions (Chords View, Track View, MIDI View, Score View, Library (Browser)
Yes Graphics that look sharp on resolutions of HD to 2k (graphics are too low resolution and are fuzzy on High DPI systems)
Support High DPI scaling mode)
YES User experience where they only have what they use, and when they need it on the screen.
YES 100% consistency of all mouse and global attributes