the .bpanelz file includes all ressources such as images etc. You can make a .bpanelz file by using the export feature of Ctrlr.
Note: When I export as a bpanelz file from Linux and include a custom ttf font, if I load this panel on a Windows machine this font is not used but reset to one of the default system fonts.
The font is included but not used: to activate it I have to open panel-edit mode and select the font for the elements that I had in mind. Only then the panel will have the looks that I had in mind. Example: my Yamaha Reface DX and Korg DS-8 and 707 panels (lcddot.ttf font used for voicename display)
Same story if I develop and export on a Windows machine and then load the panelz file on a Linux machine. Because more people use Windows I usually export on a Windows machine before making my panels public.
Don’t have any experience with OSX behaviour, so can’t tell how a Mac behaves.