"Just noticed that ERJ flights on Swiss are two-class... I'm assuming not only are all seats the same, but there is one cabin for all? Is there any difference (meal for instance) - in other words what makes C-class C-class on these flights?"

Nothing at all on board! Same seats, no curtain - it's usually less crowded up front, but many regulars tend to sit wherever they feel like or move (i.e. closer to the front than assigned) because there is no C/Y distinction. The C ticket gives you an extra 10kgs baggage allowance (30kg) and lounge access (+flexibility). That said, I find the regional planes "fun" because they (SWISS) make up for the cramped and sometimes rather noisy (Saab 2000) cabins with relatively intensive service à la former Crossair, which is why I never book anything other than Y-class on these pkanes. Two or three bar trolley runs /sandwiches / coffee / fruit and chocolates. Hot meals are served on the "longer short hauls" e.g. to Seville, Helsinki, Copenhagen etc.
You could do a lot worse!
Rgds, Marvin