I don’t believe we removed any free tier data as of yet. Some free tier customers may have deleted their own data when we announced the end of the free tier, but any that remain would just have their accounts frozen. Allowing them time to input a payment method and unlock their data.
As far as conversion rate to Pay accounts from Free, I am unaware of a report that shows this but it wouldn’t necessarily tell us who has the most data. A lot of the data was dormant and not used after we cracked down on abuse. Those accounts likely held a significant amount of the free tier data that will eventually be purged.