Plan for them in a more charitably honest sense
There was a thread not too long ago that dealt with advice for high level campaigning.
One of the pieces of advice was to make sure you deal with all personal/background quests by tier 3.
I took that to heart, I do want to conclude with their character's dilemmas, quests, wants, desires - I do not want to leave them hanging while they jump into another AP/module.
Well, I personally just don't even use any sort of published material, beyond perhaps inspiration for a location, NPC, or possibly a threat. Like when I had this party that was around mid-heroic the players seemed to want to go rove around the setting and there was an elf ranger with some background issues about elves, who had been established to be in a certain area. So I had the lord they happened to be dealing with mention that he was having some sort of problem with his northern lumber operation and maybe elves were the problem.
I figured the rest of the party might not be super interested in the elf angle, but some of them had been delving into ancient history, so I invented a thing for them to have fun with, The Vuul. This was just a type of threat that I invented from a note that there were once ancient shape shifters living in this region. So, what happened to them? Oh, they were banished to the Shadowfell and became shadow shape shifters, etc. I made up a bunch of stat-block conversions, including a big bad boss Vuul (IIRC it was a conversion of a White Dragon). Things simply went from there, I framed a scene at a wood cutter's cabin that the party ran across as they moved into the area, and a totally crazy battle happened (with the ranger leaping around the inside of a large cabin trying to avoid the Vuul who replaced the woodcutter's family while sticking them with arrows, he learned just how stupid powerful his character really was in that one). After that was a very famous 'sawmill battle' with the big bad, etc. I admit, I set up the sawmill part ahead of time, but I wasn't building up a plot. I mean, the Vuul DID have a plan, and the PCs did decide to thwart it, but nothing was completely dictated. Heck, they could have sided with the Vuul potentially! I mean, the Vuul were kicking the arses of some elves that the PCs didn't like much...
I find GMing by feet intimidating, hence me not wanting to dive straight into PbtA.
Well, I think Dungeon World is a pretty good solid game. You might try playing with some people that are experienced in running it to get a feel for the 'classic' style of DW play, but you could probably run it. You simply have to set aside notions of 'knowing how it is done' and taking the DW rules at face value. As they say, most of what DW asks you to do as a GM is actually just the same stuff all GM's do anyway.
Mostly I recommend when running one of these types of games for the first time, go gonzo. 4e is a great game this way, my GMing of 4e is 100% off the wall bonkers crazy. The world is a crazy magical fantastical and in no way mundane place. Same with Dungeon World, the world is a fantastic place, RUN WITH IT.
Nicely put.
I'm not sure I agree with you regarding 4e. What narrative element do you believe existed within 4e? I mean the path write-ups and the powers were wonderfully described and in-sync but is that all you are referring to? I get the feeling that you're implying there is more.
As for 6e, I'm not expecting much in the way or BIFTs but I will admit it would be poor form of WotC if in a decade they have not evolved the system into something more substantial.
4e has a rich set of plot hooking elements. It features an entire cosmological backstory of a vast struggle between order (the Gods) and chaos (the Primordials) which richly informs all else. It presents the players with a SERIES of defining decisions on character build, theme, paragon path, and then epic destiny, which are deeply tied to character goals, plot, and meta plot (not to mention class, which is of course the overarching choice). Even feats, powers, and magic items can be pretty defining. You are also offered additional tools like Artifacts, which are specifically designed for this sort of building up stories on the fly.
But more even than that there are specific architectural elements. Quests are often constructed by the players, and have a potentially strong influence on the shape of play. Keywords allow things to be tied together very succinctly and integrated with rules for both skill challenges and Page 42 style extemporization. A GM and players with even modest creativity and a willingness to take the mechanics as merely one possible interpretation of underlying fiction can easily do things that
@pemerton for instance seems to have regularly done in his games, like players declaring actions where they did things like sacrifice or risk the sacrifice of items or even character abilities in order to achieve specific effects, generalization of the idea of rituals as "if you are smart enough, powerful enough, and take some time you can do some pretty 'big stuff'" etc.
The strongly encounter-centered architecture of 4e is also rather ripe for story now style scene framing exercises. In fact I abandoned ALMOST all prep during my years of tenure as a 4e GM, merely writing up outlines of possible threats and scenarios, and generating some stat blocks here and there ahead of time (or often just writing up lists of ones that could be used or reflavored if I needed X, Y, or Z).