You can let the user register before sending a quote or buying.
To enable it, go to Catalog Settings > Quote Cart and set the ‘Remember fields by’ option to ‘User Account’ and save the settings.
Now you can check the Enable User Registration checkbox:
Once checked, the login form will get a registration link:
In the step by step checkout type, the first step will also get a registration link:
Once clicked, the registration form will show up: