Looking for the best way to use 2 languages in my email comms

I am based in Spain but am British and want to offer my ecommerce in several language options. In my Shopify platform I have integrated the option for English with Spanish translation but am not sure about the best way for my customers to receive their communications in their preferred language.

I am thinking that perhaps this could be done via flows by asking the customers (via 2 step signup) to opt for their chosen language for communications or by showing a different pop-up on the English page and another different on the Translated page (not sure if this is possible or if it is possible to filter the pop-up shown to the customer based on their location?) I am new to this all so happy for any ideas you might have about how to do this or if it´s even possible.

I was thinking if possible the easiest way might be to get each customer captured through a flow where there is a conditional split based on the language then I can simply duplicate each flow in each language so that there is a branch in each of the flows within the same but that separates by preferred language.