Haven't used one yet but definitely agree with the min buy being 512 GB of storage (and preferably 16 GB of RAM too) if you can afford to go there.
if you can't afford both i'd go for the 512 GB of storage over 256, given the use case of this machine:
- ultraportable
- light usage
There's nothing worse than having a sleek, lightweight ultra portable design you could use anywhere and then constantly being tethered to an external drive because you can't keep any of your work on it. Makes using it on your lap much more annoying.
MacOS applications are getting pretty big now, especially during this transition period where we're going to be seeing universal apps being more common again (essentially having native code in them for both intel and ARM).
If you do need bigger than 16 GB / 1TB i'd look at the pro line... spending much more than that on an Air unless the slightly lower weight is essential you're giving up much better speakers and display (not to mention better cooling) that you'd get from say, a 14" pro.