What happens if you switch off "Subscription" on product?

I have a subscription product and I am thinking of making it manually renewable instead of auto renewing but I'm not sure how to do that.

My instinct is to just turn off the subscription toggle but I'm not sure what the consequences will be for customers.

What happens to existing subscribers? Will their subscriptions expire or renew as they would have when they signed up?

And what happens if you do the reverse... turn on subscription for non subscription product?

What else is there to consider before I try this?