What's the best way to support both phone and tablet portrait mode?

[hardy spruce]

I'd like to ask what the best way is for supporting both phone and tablet portrait screens:

• What are the best Canvas Scaler settings and reference resolution to use?

Regarding tablets, a common approach is to keep the main UI content centered (not fully expanded), and only fully expand things like backgrounds.

I can do this by making the main UI content anchors to stay centered and not expand. Though this gives me the issue that on larger phone screens, the main UI content should still expand to the full available size. How do you solve this issue?

[analog cedar]

By making it expand ?

To be honest, making everything relative to center is really not an approach I would suggest.

You want your UI to be around your screen in a lot of case.

[hardy spruce]

Here is an example of what I want to achieve. On phones, we can utilize the full screen space. However on tablets, we don't want to expand fully so that there can be some empty space around the sides (except for backgrounds).

I can't upload images here so hope these work:
Phone: https://ibb.co/Rc4gxxX , tablet: https://ibb.co/mt9KwsM