A: No, regarding these fields Fortnox is the master. On a company synced with the Fortnox app, the fields Betalningsvillkor, Leveransvillkor and Leveranssätt are read-only in Upsales and get their values from Fortnox. So any changes in these fields will have to be made in Fortnox.
The delivery types for invoices, orders and offers can be changed in Upsales. Turn on Aktivera leveranssätt på kund (faktura/order/offert) in the Fortnox app settings. The company card then gets the fields Fakturaleveranssätt, Orderleveranssätt and Offertleveranssätt, and changes you make to them are sent to Fortnox.