I don't know if I just didn't get round to it in Opus 9, but the floating toolbar in Opus 10 is a wonder to behold.
There is just one small thing that may or may not be tweakable.
If you dock the toolbar at the edge of a screen and make it "Transparent", you can no longer "Right click" within the toolbar to change the settings.
Nor can you grab the toolbar and shuffle it around the screen. In effect, it is locked in place.
No big deal, you just go into Opus and configure it.
But you can tweak the toolbar through "Right click" so long as it isn't transparent.
Maybe it is something to do with how "Transparent" works. But if it were possible to allow that "Right click" control with "Transparent" that might help anyone who doesn't realise that they have to get back into Opus to turn off the "Transparent" setting.
Fully transparent parts of a window don't register as part of the window; clicking them will go through to whatever is underneath.
If you hold shift as you move the mouse across one of the buttons on a transparent toolbar, the whole toolbar will fade-in allowing you to right-click and drag it. (It will also display a chequerboard pattern while in Customize mode for the same reasons.)
I also saw the "border glitch"when I created my Toolbar but can't remember what it was. I think it's related to the used Background Image. Maybe it helps to set it to "stretch".
FWIW, the stuff being left behind after the toolbar's size changes (not the black border) is a bug in Windows. When non-rectangular window (like when toolbars have rounded corners) change shape, the OS does not always tell other windows that were underneath the old shape but visible with the new shape that they need to repaint. (If you drag some other window across them, they'll repaint after that.)
We try to work around it in some places (e.g. when the toolbar slides in and out it forces nearby windows to repaint) but there are still some situations where it happens.
FWIW the bug no longer happens on Vista/Win7 when using DWM, since repainting is no longer required due to desktop composition.