When setting up these two add-ons, they can be utilized together on the same order page as long as each promo product has a discounted pair, and each Stripe product created has a PayPal pair.
So for example, if you have 1 Product to sell, it might look like this with 4 products. 2 Full Price with PP Pairs, and 2 Discounted with PP Pairs:
Inside the configuration for the PayPal Plus add-on, you will pair up the product ID's for each Stripe and PayPal pair of products.
In this instance, there are 2. One pair for regular price, and one pairing for the discounted variations (used by Promo Code Pro).
Inside the configuration for the PROMO CODE PRO add-on, you will ONLY pair off the STRIPE variations.
In this example, Product 1 and 3 are paired up so when a promo discount code is used, it swaps the full price variation for the discount variation - BOTH Stripe versions.
There is no reason to create promo code pairs for the PayPal versions.
When the promo code is input, the stripe version will be swapped out appropriately.
If PayPal is selected as the payment option, then the Stripe version selected will automatically be swapped out for the PayPal variation in the final cart.
If you have any questions, please do not hesitate to reach out to support for further clarification.