As mentioned: For some things, there is no migration path because the usecase is no longer supported.
For those things that do have a Migration Path, see v5 Migration Guide | Twitch Developers
As for the “Get User Emotes” Endpoint, specifically: to reconstruct the usecase this is used for, you will need to capture the Emote Set IDs via IRC (See here) and then utilize the new Emote Endpoints in Helix to resolve the Emote set IDs. (See here)
Yes, there are inconsistencies there and there are uservoices to clarify some things. Vote for the Uservoices that indicate your missing usecases!