Julie here from Shopify Support. Thanks for reaching out!
I'd be happy to help you with updating the email address associated with your PayPal Express account. First, it would be helpful to know whether the incorrect email address is due to a typo, or if it's simply not the email address associated with your PayPal account.
The reason I ask is because when you create your Shopify store, Shopify automatically creates a PayPal Express Checkout account for the email address you used to set up your store. If there's a typo in this email address, then you'll also need to update it in Settings > General.
Then, to change the email address associated with your PayPal account, you can do so by simply deactivating and reactivating PayPal, following the instructions laid out here.
Once that's done, your payouts will be sent to the PayPal account associated with the updated email address. If your store has already processed PayPal transactions using the incorrect account, then you'll just need to contact PayPal directly to track those payouts down.
To address your second question, the answer really depends on which subscription app you are using. Each app is set up differently, so I recommend reviewing the help documentation for your subscriptions app (this can typically be accessed directly within the app, under a Support or Help section), or contacting the app developers directly. Since these apps are developed by third-party developers, they'll be the best to assist with questions like this!
Since you're selling subscriptions, I also wanted to pass along our guide, "How to Start a Subscription Business". This guide offers some excellent advice on how to create, manage, and market a successful subscription business. Hopefully you find it valuable!
I hope this helps and I'm curious to know which subscription app you're using. Feel free to follow up here and let me know.