The data that Preno sends Xero is currency and tax agnostic, and it will follow the settings on your Xero account. Prepayments and invoices will be set by Xero to your default currency (the one chosen when the Xero account was created).

All values in Preno must be inclusive of all taxes - GST/VAT. This is because Xero will calculate the tax exclusive price, and allocate your tax to the correct accounts.