If you are using PayPal standard as a payment option in WooCommerce Subscriptions, there are multiple issues.
One of the issues occurs when you change a user's subscription plan price in WooCommerce the linked PayPal subscription plan won't be updated. Thus, if the original subscription plan was for $200/mo and you change the WooCommerce Subscription to $149/mo for the user, they will still be billed $200/mo by PayPal unless you manually update the PayPal subscription also.