I was never a big fan of the Vampire/Ravenloft D&D setting, I loved the Bram Stoker’s Dracula movie in the 90’s but it doesn’t seem very D&D to me. Having said that one of the guys in my group is running a D&D game with a Vampire in it and it’s great so I’m hoping I’m pleasantly surprised.
You can pre-order Curse of Strahd on Amazon;
I really enjoyed the “Original” Gygax adventures in the Underdark, I had the compilation Queen of Spiders but you can get the individual modules in that compendium at the excellent DM’s Guild now as PDFs, from memory Vault of the Drow was the best if you just want to grab one.
My group is about half way through Out of the Abyss and it has been a blast. You should definitely check it out and compare it to it’s successors.
You can get a copy of Out of the Abyss from Amazon;