Currently, voicebanks such as Mai and SOLARIA have not been updated to fit Synth V Pro 1.8.1 better. Would it still be okay to update to Synth V Pro 1.8.1 even if their voicebanks have not been updated to fit the latest update of the studio? Thank you!
Yes, voice databases do not always need to be updated when a new version of SynthV Studio comes out.
In particular, the engine changes with 1.8.1 only apply to masculine voice databases, so those are the only ones that will be getting updates (and even then, you can still use older voice database versions with 1.8.1).