There is, but this is a conversation with a few points to consider:

• There's a philosophical viewpoint here that you shouldn't need to do performance testing. Okta is a SaaS and when a company chooses this type of service you're acknowledging that you're paying us for a bunch of things that you don't have to worry about so much anymore: availability, security (partially, this is a shared model), scalability, and performance should be considered one of these. It can be difficult for companies to trust that everything will be OK, but this is part of what you're paying us for.
• You should talk to your Customer Success Manager or Account Exec about your plans. You might need to speak to our PS team to ensure the kind of performance testing you want to do in your preview environment makes sense. Or you can raise a support ticket; with advance notice we may be able to adjust rate limits temporarily to accommodate your performance testing in preview.
• Remember that performance from our preview cells won't be exactly the same as from our production cells, as we have far more production cells in AWS than we do preview cells.
• Also remember that you must never do performance testing in a production org.
• Work with your CSM to ensure the feature flags turned on in your preview org are the same as in your production org so that the testing will be valid.