Welcome to the NS Community!
The only thing that changes is no more 40% discount for trains in off-peak hours.
You will still be billed monthly for all public transport travel, and can change back to a paid subscription any time.
Hi miss_ha,
You can use the same card. With Flex Basic you won't get any discount. You don't need to load balance on the card, you'll still get a monthly invoice with all the travel costs and this will automatically be deducted from your bank account.
The change is effective immediately.