The fact you think a campaign that says in a place is harder to prep than one that moves around, and my experience is that it works the other way around, just seems to me to mean that our brains work differently.I actually think it is harder because you should be thinking about all the connections and moving parts in that location, and how the last session would impact those things. That's prep.
But an episodic travelogue? The only consistency is the PCs and those are player responsibilities. The GM can justvroll up a town and dungeon on tables while the players argue about the division of last session's treasure. Easy peasy.
I can't emphasize enough how important good tables are for this style of play.
If the "tables" that you mention are random generation tables, the fact you find them not just useful but necessary is another indication. The best (at this point just about the only) uses I have found for them are names and treasure, and the only names I roll for these days are like shop/bar names and such.
Whatever has already happened in a game is both a foundation and a constraint for deciding what might happen next.I just do this in play, or during my walk as I build a possibility cloud. I’m not sure our brains let us show up to anything but a one-shot without at least a little percolating!