What is the best way to use banners in Google admob?

Question

Google AdMob

It's normal that Google in the guide for writing code for advertising says that the smart banner is outdated and you need to use an adaptive one, but in turn, to find out the width of the smartphone screen, you need to use a code that also has outdated methods that have no alternative, and the code is provided by Google ? What the hell to do with this Google?

Is there an option to use different constants for size for different devices, like for Banner phones, for Large banner tablets, something like what would be more correct?

If there is an article with the correct implementation without obsolete methods, then please discard