I knit fairly loosely. I use size 3's for baby and children's socks, and a size 2 for adult socks.
Cascade fixation will feel pebbly on the sole of the foot if you don't knit it fairly tightly, plus it won't wear as well when knit too loosely. No matter what size, it will still feel more pebbly than a fingerweight wool does.
If someone is really sensitive to this, you can knit it "backwards" and put the purl on the outside of the sole, but most people will be ok with it the 'normal' way.
Knit super tight it will get too thick and stiff and won't stretch. Otherwise I might go down to a 1.5, but I just don't like the fabric at that size.
I would say knit it on as small needles as you can where you still like the feel of the fabric it knits. I use the 3's for baby socks since they aren't walking around so wear and size of foot stitches doesn't matter, so I like the softer, stretchier sock. Size 3's are usually firm enough to stay on well for babies while having enough stretch and softness to make them easy to put on and not binding. Remember that is size 3 in the tension I knit... you may find a different size works.
How you hold the yarn (how much it stretches as you work it) and your tension will make a difference in needle size chosen. Don't be afraid to start the cuff a couple of times and see how you like the tension and frog and retry a different needle size if you like. You might also knit a small square of stockinett.. it won't have the same exact tension as knitting in the round but will give a feel for how the yarn works, plus the elastic will take care of most small tension differences.
I used 2's for my grown daughter's socks and they have held up decently well.