This post explains how to setup RFQ-ToolKit Plus to allow customers to buy now or request a quote at WooCommerce checkout. Customers can purchase normally at checkout or request a quote. You can optionally put a minimum purchase requirement as a condition to request a quote.
Step1: Select RFQ and choose to show prices.
Step 2: Select option 5 to activate the rule.
With this setup, your customers can checkout normally or request a quote at checkout.