The exchange rate you receive on each transaction will depend on the payment method used for payment. Stripe handles currency conversion based on the bank accounts you have set up in your Stripe account. Read more details on the Stripe website.
In terms of how you charge customers and receive payment, below are some details.
The WP Stripe Global payment form is flexible and can be customized to charge your customers in any of the 130+ Stripe supported currencies. You can lock the Credit Card payment form to charge in any currency you want or let the customer choose the currency they want to be charged in with a dropdown box. Stripe handles the currency conversion from there.
Check out the shortcodes for details on customizing the payment form.
Cross-border payments with WeChat Pay use the spot exchange rate from the China Construction Bank or China Citic Bank. WeChat Pay transactions are paid by the customer in CNY and are settled in the default currency of your Stripe account.
WeChat Pay handles exchange rate fees internally.
More information can be found on WeChat's website.
Alipay payments are similar to WeChat Pay in that your Stripe account will receive the amount in your Stripe default currency.