but I will defiently use B4Xpages for the future
Very good that you choose for that route in the future. Another piece of advice, use the B4X elements as much as possible in your current program. You can then easily reuse your current program solutions in the future with very few adjustments in a future B4XPages solution.
Erel's advice is to develop B4X programs in B4J. My experience is that a B4J program is therefore that it is very simple to convert a B4J program to a B4XPages with very little adjustment.
And regardless of whether or not you program a solution for multiple Operating Systems (OS), working with a B4XPage has many advantages. Because a B4XPage is essentially a class that is stored in a separate file, you can reuse the solution from any B4XPage much more easily. Because you actually cut your program code into different modules that offer a certain functionality.
And if you make an improvement or extension to your B4XPage, that improvement and function extension is immediately applied to all B4XPage programs that are linked to that B4XPage.
Only if you want to release your B4XPages program under a different OS, you will only run into the differences between those OS and you can make an adjustment in your program code to provide a solution for one or more specific OS-related issues. This gives you an unprecedentedly large flexible growth path.
Good luck with your program development.