Is it possible to set a default sales order form depending on the customer selected? Is this possible without scripting?

you mean sales order field? If so i'd suggest to create a custom field on the customer and have workflow set field value to be the same value as in that field on the customer - hope that makes sense lol

Sorry. I meant sales order form.

Should be able to do that with a WF, using the after field edit action, with the condition of if customer X, then set field value custom form = Y ? That should work