remember that Y axis is positive down, so if the "up" vector is positive Y, you're defining things flipped. The reason for this is obvious, so that the view-port of construct's editor lines up with Q3D's, and of course maintaining the fact that everything use right-handed cross products / coordinate systems (which is the de-facto standard in most 3D fields)
Viewports only support full transparent / opaque backgrounds because of how they're rendered. It's not something that can easily be changed due to limitations in three.js/webGL and Construct. Doing this was the "best" choice I could make in terms of speed as well.
Q3D Master has a lot of deprecated features, that have niche uses you normally would need. Always look at the actual available objects first as they're better optimized and require less micro-management from you and are mostly guaranteed to work. I have no idea how you were even trying to pick the Q3DModels with "change" parent as they don't have any internal ID's available to Q3D.
That's weird. I haven't tested anything in 214, but that bug in particular means something fundamentally isn't working. Could be how you installed the plugins, or could just be how you set up the scene, I have no way of telling. You always need an instance of Q3DMaster in the layout to do anything at all, if you're missing it that kind of bug can occur, since Q3D isn't loading any of the necessary components (In this case the ENTIRE three.js library isn't loaded for likely this reason). Do you get that error trying to run examples?