I only things I have used multiple years are mainly for DnD 5e 2014:

• Monstrous Races - a supplement that turns everything from official Monster Manuals into playable races with a lovely commentary about how these were balanced.
• Conflux Creatures - just better creatures, this is the first thing I do is to replace monsters of premade adventures with the Conflux ones. They are just much better experience compared to sacks of HP that most 5e monsters are. There is no need to read “Monsters know what they are doing” when the stat block pretty much does it for you.
• Creature Loot by Medieval Melodies: https://medievalmelodies.blogspot.com/2017/06/creature-loot-intro.html - lootsies + crafting for all of the creatures.
• The Alexandrian: thealexandrian.net for reviews, advice and remixes of official campaigns
• Official WotC products besides the campaigns: Fizban’s Treasury of Dragons for all of the Dragon Lore

Had a wine & lore dump session with a partial group in our DnD 5e game. All of the speculation of my players lead me to realize how well historical events I have come up with fit to the official lore from Fizban’s Treasury of Dragons. I got also to introduce a NPC who will come relevant in three levels when they can tackle one of the better adventures from Candlekeep Mysteries.

We also played Alice is Missing for the first time and while it didn’t meet all of the hype, we had fun evening and I must play it again to get some more familiarity with the storytelling it assumes from the players.

I would say that most of the wisdom in Trajectory of Fear (https://nerdsonearth.com/wp-content/uploads/2020/03/Trajectory-of-Fear.pdf) would work here as well even though it’s about Horror.

If you think about the steps presented there as of Unease, Suspicion, Anticipation and Revelation then the advice should work really well.

“I can’t really do the same with my homebrew world which has very little in common with the real world.” I don’t think that is necessarily true but it requires the players to have a proper understanding of what is normal and expected.

Zoo and museum tickets

I would say that many Mind Flayer villains are quite interesting because they are Mind Flayers.

Alexandrian had some interesting thoughts about what to avoid when running rival party in his Call of the Netherdeep -review (includes spoilers about the adventure): https://thealexandrian.net/wordpress/48216/roleplaying-games/review-call-of-the-netherdeep