Our app has an auto-conversion feature which uses geotargeting. For your customers, their default currency will be their local currency.
However, you can change the default currency. The only option at the moment is your store base currency, which you can turn ON/OFF in the app.
When it's enabled, the currency dropdown menu displays your store base currency by default, unless website visitors select other ones from the dropdown manually.
We attached a screenshot for your reference.