Please note, "Multiworld" and "Online" are two different terms for two different game modes. You do NOT need Multiworld to play Online with your friends. This is a setting only used for Randomizers.
Multiple players play in different worlds collecting each other items and working together to beat a randomizer seed. Each player has their own chests and gifts to collect to send to others. Inventory does NOT sync, items and quest flags are separate. Prior planning is required, this includes number of players and committing time for your group to complete a seed. Players need to patch their own ROMs corresponding to number of players so that nobody is using the same world ROM.
Multiple players work together in the same world to complete a seed in a simulated Online co-op experience. Players all have the same chests and gifts to collect and share them. Inventory DOES sync, items and quest flags are shared. Players are allowed to come and go as they please regardless of who did what checks in the seed. Players can generate and use the same ROM to play together. Players CAN see each other with OoTOnline.pak enabled and can use custom models.
Ocarina of Time Randomizer
1.) When creating multiworld seeds, the person who generates the seed will have to set the player count to the number of players decided beforehand on the generator.
2.) After setting your player count, choose whichever settings you want to play with, then generate it.
3.) Send your seed link to the other players, and remember which player number everyone has chosen to be.
4.) Each player will then have to patch their own ROMs with a corresponding player number, so that no one is using the same ROM.
5.) Each player puts their own ROM into their /roms folder
6.) Each player can now start ModLoader64, put in the exact same lobby name and password, and ensure that the correct ROM and OoTOnline are selected (players can also choose whichever cosmetic mods they'd like to use)
7.) After starting the emulator, ensure that the seed hash is the same in the file select menu before making your file. The hash is the 5 item icons sitting above the file select menu. If it is not the same then somebody either generated the wrong ROM, or they have selected the incorrect ROM from within ModLoader64.