I know that technically superfine is for needles 1-3, but I was wondering if anyone could tell me from experience if a 4 would work without leaving it too loose.
Depends how tightly you knit and perhaps what you’re making…
But those recommendations are just a typical size range to consider for the yarn, not requirements. You can use any size needles you want with any yarn if it gets you the gauge you’d like.
I would be making straight needle socks, and I am neither a tight nor loose knitter.
I’d say do a gauge and see if you like the fabric. But looser fabrics aren’t the best for socks.