I replaced my aging NUC with a Minisforum SFF box and am also very happy with it. Footprint is slightly larger, but actually find it much quieter. The NUC was basically silent 90% of the time too, but it had an annoying high pitched whine if you were doing something very CPU-intensive.
Depending on model they can support up to 2 m.2s and a 2.5" drive.
Yup, if you just use a couple different IPs in a given time they will arbitrarily mark you as requiring a license.