You can use alot of it. The main difference is the ties to the widget events. They are coded different between qt and glade, but it wasn't very difficult to make the change. The nice thing is, if you use qtpyvcp widgets, you can write expressions for rules to change widget properties in the vcp itself based on linuxcnc status without having to do it in your python code.
The big thing I ran into was moving from debian 9 to 10 and linuxcnc 2.7 to 2.8 at the same time I switched from glade to qtpyvcp. In hind sight, it looks like glade and qtvcp are more supported by linuxcnc and python 3 than qtpyvcp is. That may be something to consider before proceeding.