Another element of “formality” is the inclusion of butler service, which many people enjoy and appreciate, but some of us prefer not to have this.
I greatly enjoyed my Uniworld river cruise (2017 vintage), it ticked all the boxes for food, service, excellent guides, “like a local” opportunities, comfortable ship, and fun and companionable fellow travelers.
I’ve also sailed with Oceania and Silversea, the latter was one of their expedition cruises. I enjoyed Oceania a lot more than I thought I would, I’d worried that the ship (1200 pax) might be too big. But it wasn’t, I never felt crowded, and that cruise also ticked all the boxes. I really enjoyed the people I met on that cruise (Baltic).
While I enjoyed the Silversea expedition cruise (the itinerary was the Russian Far East and the Aleutian Islands), the mandatory assignment of the butler made me nuts. I didn’t really have anything for him to do, and this made me feel guilty, to the point where I would try to avoid running into him, because he was always asking , “what can I do for you?”, and I never had an answer. Then he started looking for things to do for me, like shining shoes and “straightening my room”. When I finally did have something to ask him about (a camera issue), although he tried very hard to be helpful, he wasn’t able to address the situation, and a fellow traveler provided assistance instead. Honestly, this “hovering” is what has kept me from rebooking with Silversea, because otherwise I really like their product! (And I thought that Silver Explorer was a sweet ship, just right in size.). So if you think the butler service feature would be “too much” for you, you might wish to keep that in mind, when looking at alternatives. But if butler service sounds good to you, then Silversea has some really nice itineraries.
Perhaps because it was an expedition cruise, the Silversea “dress code” was not strictly abided by. People wore what they were comfortable with, and many did dress “a little better” for the Captains Dinner.