I've combined all the Feed the Beast Mods (FTB) together because they work well together and can rely on each others for full functionality. They're what I currently use for a modded Minecraft server! My main complaint is the lack of documentation for certain mods. Just something to keep in mind for consideration.
FTB Backups Game Versions 1.12, 1.14 and 1.15. 1.16 Creates backups for servers when players are online to reduce clutter.
FTB Quests Game Versions 1.12, 1.15 and 1.16 This mod is great for those who want a server with quests. It makes it easy to create quests for players.
MINECRAFT
FTB Chunks game versions: 1.15, 1.5 This mod comes with its world map and minimap. You can also claim chunks. Only those the player allies with will be able to interact or affect blocks in the claimed area. FTB Teams are highly recommended for full functionality.
FTB Teams Game Versions 1.15, 1.16 This mod allows for teams to be created. On its own, it's not very impressive, but matched with FTB Chunks and FTB Quests, servers run smoothly.
FTB Ultimine Game Versions: 1.12, 1.15, 1.16 This is a great VeinMeiner alternative for newer game versions. Players can harvest multiple blocks simultaneously by using a configurable key. You can also configure a whitelist of blocks for the server!
FTB Essentials Game Version 1.16 This mod adds utility command that are essential for running and maintaining a server. It allows players the ability to teleport to each other, change nicknames, establish homes, and much more!
FTB Ranks Game Versions: 1.15, 1.16 This is essential if you want to enable permissions on a server. It is possible to set ranks for new players and moderators.