Hand 1 : I prefer to lead the river for 30-35 and fold when he pushes for 25 more (as ridiculous as it sounds I think it's optimal) since lots of 2 pr hands will pay you off but will pretty much never bluff a river lead. I can see how this can be donkish but I hate it when villain checks behind with a QJ-type hand on river.

Hand 2 : without knowing villain's tendencies it's impossible to give advice. Vs. some villains it's an insta-call and others it's an insta-fold. It's just so read-based that there's almost no grey area once you know who you're up against.

Vs an unknown I'd either flip a coin if you're feeling nitty or call. I'm usually about 65-35 call-fold I think vs an unknown (don't know where I came up with that but it feels about right).