I am trying to get a relative sizing for my Canvas App that I embedded in one tab with a one column format. I worked on my app, checked the size and by default this is what I have:

And when I go back to D365 to test it, this is what I see:

It's HUGE......I can make my fonts smaller and add more content (I do need that either way) so the width would work for me but the length is the problem - I have to scroll a lot to get to the bottom.
I would manually change the size of the app, but I do not know what will happen if someone else's screen has a different size.
How do I get the relative sizing, where I do not have to worry about such issue? And that question is valid for the powerapps in general, as I noticed on a tablet app that if I resize the size of the web page, I get scrolling instead of automate relative positioning.
Please help.