Hi, and welcome to the forum!
As far as officially, "normal" is about as large as I'd like it to be, both for performance and gameplay reasons. I also wouldn't necessarily count on "small" sticking around; I don't think it's much of a performance benefit, and that's the primary reason hat setting exists. Modding-wise, it's definitely possible to make it larger, though.
In data/config/settings.json, there's:
"sectorWidth":164000,
"sectorHeight":104000,
You can increase those to make the map itself larger. The number of stars will, iirc, stop at 100 constellations (that's also moddable, but more involved), so it'll go up some if you increase the sector dimensions - since the current Sector, iirc, generally has <100 - but if you say, double the width and height, the constellations will be considerably more sparse.