From the context, it is obvious though, cheese is typed as チーズ in katakana.
ツナか牛肉とチズでサンドイッチを作る。
Say, now we know we are preparing sandwiches. If we have "tuna", "cuts of beef" and "slices of cheese". In this case, it is normal to think to prepare sandwiches with the combination of “beef or tuna” and “cheese”. Whereas now we are seeing a can of “tuna in a water” and a can of “beef mixed with cheese sauce” at the supermarket, you might think it as preparing sandwiches with “tuna” or “beef and cheese”.
Edit: The comment is too small to see what it is.
Yes, it's context dependent. Say, you go one-day sightseeing, (富士山か東京と横浜を観光する) Go sightseeing for Mt.Fuji or Tokyo and Yokohama. It depends on how you define sightseeing, what transportation you use and where you stay. If you use a bullet train and just taking a photo of Mt.Fuji, it is possible to go sightseeing Mt.Fuji and Yokohama within a day. If you do not use super- express train like a bullet train, go sightseeing for Yokohama and Tokyo within a day is more realistic.