Field Service is really just an extension to the Projects app.  So you can use Field Service features with projects as required.

You could have a Field Service project for doing quotes and then create a sales order from which Odoo can create a project - and you can book time against that task.

Or possibly you start with a sales order with a product that is set up to create a project and a (free of charge) task for the on-site quote.  You need to confirm it, so it creates the project and a task. Then later if they go ahead you add more billable services (which Odoo will add as tasks to the project).

field service might work better because it will create a sales order directly when you add products to your formulary maybe a futher look into the real case would help to untestand better the requirements