Hi @Ynax I don’t think this is really a Bokeh-specific question, by which I mean that there is nothing about Bokeh that should overtly dictate your application design decisions. Conversely, things that do directly inform software design are: your own requirements about what you want to accomplish, where you need flexibility or extensibility, what trade-offs you are willing to make for performance, ease-of-maintenance, and agility, etc. Does it make sense to have a class for layouts? The answer could equally be yes or no, depending on the details of your project.
Without more context, these are all broad and general topics, and I think you might be better served asking for general software design advice around your requirements in a larger and less-specialized forum.