Here’s a helpful review of Diablo III: Eternal Collection for Nintendo Switch, specifically regarding the NSP version, language options, and update (update/patch) situation.
For the average English-speaking player, the base US or EU Eternal Collection NSP with standard updates is sufficient. However, for polyglot players, expats, or JRPG fans who want the original Japanese Diablo voiceovers (a surprisingly different performance), the Language P Update is essential. diablo iii eternal collection nsp language p upd
If you have installed the wrong language pack or need to save space, you can remove them through these steps: Here’s a helpful review of Diablo III: Eternal