You can show confirm button for specific group and you can do it as below:

Using Studio App

You can use studio app (if purchased), open any RFQ in form view and then click on studio icon beside the activity icon at the top of the page and once the studio opened click on Confirm button and in the right side you can set the "Limit visibility to groups" for the group you want.

Using Xml 

If you are not have studio, you can do it from xml as below:

Hide/Show Confirm button based on user (Purchase Order) | Odoo

Hide/Show Confirm button based on user (Quotation Order) | Odoo