I tried to reply you via email, but email is INVALID. Looks that you opened website when I was online, thus got automated greeting, but messaged me AFTER I turned off computer… and I do switch to invisible to appear offline 10 min before turning off computer, to prevent new visitors to be greet and allow visitors who were already greet to message me, but this was not enough for you as you messaged me after 23 minutes. Willow Creek and Oasis Springs are included in The Sims 4 base game, they are NOT secret worlds. World article including List of lots is copied from including any errors existing in their website.

Due to same reason I did not made an accurate Excel list of lots in each world as I did for The Sims 3 worlds. Please DON’T ask recommendations what expansion packs to buy, this depends by each person preferences and personally I did NOT played The Sims 4 (other than when EA GAMES allowed playing base game for free for 48 hours) so my answer will be irrelevant. The Sims 4 does NOT offer additional download-able worlds or any tool for players to make custom worlds, like Create-a-World for The Sims 3. Click each world name to see list of lots and families. Here is the list of worlds shipped with The Sims 4 base game and expansion packs (19 worlds as July 2021).

The sims 4 expansion packs list