I also like a mixture of encounter and story progress XP. If you feel like the players gain too many XP you could give them some short time benefits instead as reward from time to time instead. This way they get rewarded but will not level up too fast. Some examples:
- they get a discount from a merchant
- the players can use an NPCs house as safehouse for a few days
- the can use an expensive transportation method for a single route for free
- the local smith will repair all their gear for free
- the players are invited to an exclusive event
- the players are provided with a local guide for a day giving them a bonus on some checks while travelling through the region
If you are hosting a campaign where the players have their own piece of land or business they can also be rewarded with "fame", leading to more NPCs willing to work for them.
Love those ideas. I’ve used fame as a negative when they’ve got too murdery before!