Hey there Marquees14,
We'd like to team up with you to help answer your questions regarding your saved card details.
For your question about verifying your payment details, even with a free app, this is expected behavior. Sometimes it'll ask to confirm your details, even with free apps, to make sure your information is up to date.
Regarding checking for which subscriptions are active, this link shows how to do this, and even includes a link near the top if you don't see any active subscriptions: How to cancel a subscription from Apple
Just in case, here's how to Change, add, or remove Apple ID payment methods.
This last link has more details about what we explained earlier, but we recommend reviewing it in full: If you can't remove your last payment method or use no payment method with your Apple ID
Have a good one!