I made the collar rib with twisted rib with 5.5mm
k1tbl, p in orde to obtain a tighter collar but I don’t like it very much. However I won’t unravel the project just for this.

As in other Sunday sweater/cardigans I knit in the past I preferred to increase with m1R instead of the the m1k, described in the pattern instructions.
This type of increase leaves virtually no hole while the m1k leaves a little hole.

Wrist cuffs and bottom rib: k1,p1 with 5.5mm