Well, layout design is very suptile in B4A.
You have devices from screen sizes of about 4'' up to 10''.
Then, you need to define what you want to display at the same time on a same screen.
Do you want to show the same layout, designed for a 4'' screen stretched to fit in a 10'' screen ?
Probably no, for me it's none sense!
So you need to define the usage of your application, for phones and tablets or only phones or only tablets.
Depending on this. the layout design will, could, be different!
So, YOU need to decide what YOU want to display at the same time on one screen for given devices !?
It's a simple phrase, but all the difficulty is here.
Just as an example, I had written, quite some time ago, an application to read mp3 files, a juke box, not published.
The first application was for a friend of mine having a tablet.
So, I designed a layout for tablet and all was fine.
But, then I thought, it would be interesting for me to have it also on my phone.
So, I wrote an application for phones.
But, maintaining two applications with almost 80 to 90% of same code is crazy.
So, I merged both applications into one, but, defining different layouts for phones and tablets working with one Activity and Panels.
On phones, I display one Panel in portrait orientation and on tablets I display two Panels side by side in landscape orientation with small adaptations.
It needed quite some adaptations for the Panel management, but at the end it works fine for about 5 years now.
And finally, I used it more on the phone instead of a tablet.
Sorry for the 'long' story, but it illustrates the problem.