The plugin performance is more-less equivalent with the overall server and the wordpress setup performance. If you haven't done so, I suggest checking the Fine tuning the search performance chapter in the documentation. It gives you all the greatest tips to improve the overall search perfromance via configuration.
For more detailed explanations you can check chapter 18 in the documentation.
If you tick the “Set as private reply” checkbox under your following reply, then you can share sensitive information as well 🙂
I will check the label issue as well, once I can log in to check your site.
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