The new M1 (Apple Silicon) Macs will run iOS and iPadOS apps natively, straight from the App Store. No need for conversion. Keep in mind these apps are built for the touch interface, but Macs do not have touch screens. This means they may not be as convenient to use as they are on iPads.
I have not tried any iOS or iPadOS apps on the MacBook Air yet. Most of the apps I want on the Air have native Mac versions that sync with the iOS versions (usually through iCloud). So far those include Fantasical, Reeder, Notability, and Tweetbot. Also, the Microsoft Office suite. My Office 365 subscription includes a license for one laptop/desktop install.
Of course all of Apple's apps (at least all I use) have native Mac versions.
Xcode is strictly for app development. Even if you wanted to convert an iOS app to Mac, you would not have the necessary files to do it unless the developer (for some reason) gave you the source files. Even then, you'd need to do some extra work.
I want Xcode because I'm in one of my "I want to make an app" moods." It will likely pass without me doing more than dipping my toes and deciding the water is too cold, as it has in the past; but hope is eternal.
Thanks TP for the additional information - if I do get an Apple Silicon laptop in the next few months, the main reason would be for a replacement of my 7 y/o MBPro which will not take Big Sur - although I knew that the M1 chip would run iOS/iPadOS apps natively, the 'touch screen' was of course the issue - as an example, I have only a half dozen games on my iPad Pro (couple of Solitaries, Sudoku, etc.) and all involve the touch screen. Dave