I posted this question a while ago coming to the conclusion, that one should just leave the „state“ in APVTS alone (even though it clearly advertised in the documentation. JUCE Team haven’t responded yet). AudioProcessorValueTreeState with custom ValueTree
„Is there a simpler solution“: I think yes, just use a different ValueTree were you know what happens (and what is thread safe).
Concerning your concrete problems: it really does sound a lot like the DAW is creating your plugin and editor before the state is set. Although you seemed to have debuged the method calls? I think it would be beneficial if you could share a bit more code so we can understand what exactly is going on.
Having the editor listening to the valueTree is (in my opinion) a must have feature. Imagine the DAW changing your state (for what ever reason), you‘d want your editor to reflect what’s in the state including the bounds of your editor window.