From the Xcode 11 release notes:
NSView and UIView have a layout mode option in the Size inspector to explicitly opt into “translates autoresizing mask into constraints”. The default setting is “Automatic”, which is the existing behavior. “Automatic” implies that “translate autoresizing mask into constraints” is off when a view affect by constraints in the storyboard or .xib file, but on if unconstrained. (37352354)
Displaying NSViews and sub-classes will work with views that have no constraints. Whether you select automatic or translate autoresizing mask into constraints in the Layout menu you will see a lot of layout errors, at least in a window with a lot of views.
The tool that is included in Xcode 11 to add these resources is severely broken. My project has15 small panels with a few UI elements. I was able to add layout constraints to these with the tool but it took several tries. The tool sometimes did things like greatly increase the size of the window or add layout constraints to only some of the NSViews. My application has one window with a lot of NSViews. Neither the tool nor Interface builder can deal with this. In the window with a lot of NSViews I tried to add layout constraints to all of these, to some of these in a column and to only single ones and the tool fails to do it and asks me to report the problem to Apple bug reporter. It looks like you will have to ignore a lot of warnings until Xcode 11.1.