I've run many 5E sessions in Arden Vul. I laid an overarching story plot that had the PC’s play 10 sessions to get to level 3 before they found out that some slavers had sold various family members to the cultists who reside in the ruins. They have explored most of the northern sections of level 3 as well as the tower of Scrutiny and excursions to level 2, 4, and 5. The PC's have just used a potion of fly to explore the great chasm. They were surprised to learn that there are several entrances on level 2 and 3 they missed and that it goes waaaay deeper than they ever imagined. They just cleaned out the Halfling thugs on level 3. They have recovered some family members, and are keen to explore the boundaries of the ruins. There is plenty of foreshadowing and NPC factions. They have had minor interactions with the Beastmen, Sun Scarred Knights, Goblins, Daltons Darlings, and have seen the Pukel-manders. We’re having a lot of fun so far! I think the key to running this setting well is to give the players enough of a motive to begin exploring, and then try to keep up the preparation required to have fun and fulfilling game sessions and just see where the player curiosity takes them. I also have some other stuff standing by, including quests for the Blue Lady in case they want to do other activities entirely. Thye hard part is trying to guess where they might go next. They have changed their minds three times now and I've mostly had to wing it.