No extra fee for the specialty restaurants. Book early, though - the specialty restaurants are not all that large.
And, yes, Viking is far more sophisticated than Princess. Viking's target audience is people who want to learn about and have experiences with other cultures.
Regarding cabin and class - I book whatever veranda cabins have the best price at the moment. I do not care to book a cabin on the lowest deck because I want a full-size window. We did book one of the lowest priced cabins once when money was tight - it was OK, but I really like having a big window and, in warm weather especially, a veranda.