I’ve been on 2 cruises with a total of 6 in our group and 2 with a total of 4. Our dinner seating has always been sized to our groups. Lunch and Breakfast are open seating so if you eat in the dinning room, you will often be seated with other people since they tend to use the 10 person tables.
It works out pretty good. You eat dinner with a group that you are comfortable with but during shorter meals you have a chance to meet other interesting people.