vdiffr | Visual regression testing and graphical diffing | Testing library

I am trying to make some GUI for my CRAN package

1. some f function that locally launches a popup with a few params rendering a few outputs, like launching locally a simple shiny app.
2. the popup permits to select the parameters easily and then a "validate" button triggers the return of fwith the selected parameters, like shiny with stopApp

I have already done that with shiny but i think the result is a bit unsatisfying because shiny apps are slow to launch and stop (if there is an object to serialize i guess).

I have seen that some packages, like vdiffr, seem to answer this problem by making a list of the objects to change, thus they only launch shiny once to change everything with some selecter. If possible I'd like to avoid this solution.

So the question is : is there some kind of GUI framework more convenient than Shiny for this (only local, fast launch and fast return) ? Or some fine way to do that, that is light enough (I don't want to make my package to be extraordinary heavy for a small popup) ?