Applying custom resolutions

[Pmcnaught]

Sorry if I posted this in the wrong place before.

I have a galaxy tab active 3.

I find when I reduce the resolution width I cannot reduce the height sucessfully at the same time, even when default aspect ratio is disabled.

I understand there might be limitations on possible resolutions due to hardware and software. Is there any way to know which resolutions would be successful?

I would really like to have more flexibility with reslutions but witout rooting my phone. Do you have any suggestions?

Thanks for the App, I still find it very useful

Peter