If your looking for the best mod pack in 2021 you might be surprised with my answer.
After spending a long time testing and adding mod packs to servers i can still say by far it has got to be RL Craft.
For a Tutorial on adding it to your server you can check out this link.
From the land generation that actually allows you to play it on a server with out as much lag as other mods such as Valhehsia or Pixelmon.
Not only that it has (in my opinion) the best mobs in a mod pack, from fire or ice breathing dragons to fairies that heal you in desperate situations.