Hello!
You will get upgraded wagons in the main game mode that carry many more cards than the default one.
Theres also storage chests in the game that you will discover as you progress as well + something else that can boost the max card limit that i dont want to spoil here :)
You can revisit any location youve been to but the waves will get tougher the longer you stay. After wave 10, the location becomes depleted and you will have to move on to another location.
If you discover a village, it will become a raid zone, allowing you to send your toughest minions there to conquer it. This will allow you to unlock a rewards of your choice (among 3 random ones) like new recipes and artifact quests. These get tougher for each raid zone you find and finally you have to find and beat the castle raid zone which is the final encounter for a run. These runs are procedurally generated and the map looks different each time.
The castle unlocks certain features that you cant get anywhere else. Like a library to see all cards in the game, and additional artifact slots that allows you to select multiple passive buffs between each run.
Resources in a location will not continue spawning forever since each type has a max limit. So if an area can spawn up to 3 trees, you will never see more than 3 at a time. Once you deplete them, they will eventually respawn at another spot.
Hope this was helpful!