Regular yogurt contains something like 17-25g sugar per serving while greek yogurt contains something like 7-11g of sugar per serving; so go with the greek yogurt if possible. It is more expensive but is worth it!
I couldn’t make kefir correctly myself such just bought a pint of it last night; the pre-made stuff should still be effective but not as effective as making it at home.
The sardines should be OK as long as there isn’t any additional ingredients on the label. The salmon should be completely OK as well.