I've found it useful to do layouts in B4J, where you can resize the WYSIWYG window to get immediate feedback on what will (likely) happen on device screens with different aspect ratios and sizes (to a lesser degree, if using AutoScale).
The new copy controls between different platforms feature will probably make this process easier. Having said that, what I actually do is run a B4J program that generates Designer Script from a variety of aesthetic master variants, that I then paste into the script area of the corresponding B4A/B4I layout, which works a treat but is obviously a bit tedious.
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