GRACE Periods - in Configuration and in each PLAN

I know that this has been discussed before in the forum, but the more I read those responses the more confused I am getting.  

All of our plans have a fixed expiration date of Dec 31 in the relevant year based on their length.  We aren't using recurring, upgrades or pro rata payments, just renewals.  
So if someone joins in December (any day even Dec 30) their subscription will run out at the end of the calendar year.  This may change but this is how it is right now; there are benefits they receive that make this worthwhile.
We want them to be able to renew their current subscription for 15 days into the next year; so the expiry date is Dec 31, 2021, but we want them to be able to renew until Jan 15, 2022.

We have the Grace Period in configuration set to 15 days.  What does this accomplish?
We also have Grace Period set to 15 days in each individual plan.  What does this accomplish?
Are these correct for what I've described above?
Can they still log in from Jan 1 - Jan 15 in the 15 days after expiry and view what they normally see or does this grace period just apply to subscription renewals?

Thank you.
Darlene
p.s. this is our first year with Membership Pro and Joomla; we went live with the new website on April 1.

Hello

1. The Grace Period in Configuration is used for different purpose. It will give you that extra 15 days for your subscription. So if your subscription end date is 2021-12-31, at that date, the subscription status will be expired. However, with Grace Period set to 15 days, the system will still leave your subscription active until 2022-01-15 (basically, you have extra 15 days for the subscription)

2. The Grace Period in the plan is used for different purpose. Normally, with your setup, if someone sign up on 30 December 2021, the system will still set your subscription end date to 31 December 2021 (which is not right, I think). So if you set grace period inside the plan to 15 days for, anyone sign up in the last 15 days will be expired in next year. So if you subscribe on 16 December 2021 for example, your subscription will be expired on 31 December 2022, not 31 December 2021

Hope it is clear to you.

For your need, you might not need to setup grace period. In Membership Pro, users can renew their subscriptions anytime they want

Regards,

Tuan