How many devices can the unlimited plan support?

It supports unlimited use of your virtual devices, but the docs do not state a specific simultaneous-device cap for the Unlimited plan. For Genymotion SaaS, the limit is plan-dependent, and only the Pay-As-You-Go plan is explicitly capped at 2 devices by default. See How many devices can I run simultaneously? and Genymotion Android Emulator in the Cloud.

Are you asking about SaaS, Desktop, or Cloud devices for your setup?