Regarding Locale's, I think, if you install the program with English as Unicode language and English as display language, Using Locale Emulator (after setting it to Japanese locale) should enable you to use it normally. I think I messed up one time bc I installed Voiceroid+ Yuzuki Yukari EX using japanese as unicode language and switched it back to English. I got an error and it won't run.
After that I decided to just make my laptop run on Japanese language as a whole (JP as unicode lang, JP as display lang, and JP as location/time setting) since I don't want the headache. Maybe other user can provide more info/clarification for Locale setting.
Next, in case of the choices you presented, you have no choice but number 1, "Voiceroid+ Yuzuki Yukari EX". Why? Because before the "Voiceroid+ EX series", there's a "Voiceroid series." Now they're no longer available while people that still have them can upgrade to EX series by buying what you label as number 2.
After Voiceroid upgrades to Voiceroid+ EX series, come Voiceroid2 series. Personally, I suggest you get the VOICEROID2 version if you can afford it and don't mind the emotion preset.
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My Kotonoha Akane/Aoi Voiceroid2's version have English install manual attached so I think Yukari's Voiceroid2 will also have them to make it easier for you if you cannot read Japanese. Voiceroid2 also have
Better interface (in my opinion), though this also means more complex interface compared to Voiceroid+EX
Can save audio while saving the line they read as .txt file (Voiceroid+EX have to use Voiceroidutil to be able to do that)
They also can save preset (voice setting, such as pitch, reading speed, etc.) where Voiceroid+EX user have to use kotonoassist if you want to do that.
I'll be aiming for the not-"upgrade" offers then. I wanted to know which version to get in general, not just Yukari. I'm sorry I didn't specify the problem.
I'll try to make it work using the Locale Emulator. My only concern is that does the VOICEROID+ work completely fine with all features like regulation of voice intonation? It's the most important for me. On the other hand I'm not really interested in saving my work, because I'm used to do it using third-party programs.
I've been using VOICEROID2 already (Kizuna Akari) and the newest version of Yuzuki Yukari is on my 'to buy' list, definitely. :)
Ah I see. I don't understand what you mean by features like regulation of voice intonation, but Voiceroid+ex is just Voiceroid 2 with simpler interface and no emotion setting (happiness etc.). If what you mean by that is related to using Voiceroid for DAW/with Kotonosync, I can't help you since I know nothing about music and I'm not a vocaloid producer. Hopefully someone else can answer that.