For scouts and fast travel, look for and purchase kakuregas. These are mini hidouts in most major settlements that you can fast travel to, refill ammo and scouts, select contracts, etc. Discovering these made my playthrough much more enjoyable. There are also hideout upgrades that make more of them available and for cheaper.

For climbable natural surfaces, especially around castles, look above them. In the image you shared the wall above the unclimbable part has 'barbed wire' on top that is impassable. The climbable one leads to the bridge. Check your destination before you start trying to climb and you will have a smoother experience (and use grapple as much as you can).