I find it really depends on the watch.
I have a 19 cm wrist, just under 7.5 inches, but with a curved profile so a smaller "flat" spot on top. I've owned watches from 36 to 45 mm, with lug-2-lug anywhere from 42 to 52 mm.
At the large end I've found that I don't really like anything over 40 mm diameter, and anything L2L over 46 has to have a fair amount of downturn to the lugs to fit comfortably.
On the small end, however, things really depend on the watch.
For example, I had a Grand Seiko SBGF021 that I really wanted to keep as a perfect GADA watch. Yet even though it has a 38 mm case, it's oversize bezel, smaller dial, and tapered 19 mm bracelet meant it fit very small on my wrist. I never got used to how it looked and ended up selling it.
On the other hand I have a Bertucci A1-S that is 36 mm, with a L2L of 45 that fits great. It has an overbuilt case for protection, and a 20 mm lug width, and somehow it never seems too small.
I've found that, having tried many watches over the years I have a pretty strict upper size limit, but am more flexible at the lower end.