It depends where your origin is, where your users are (near 1 PoP? 2 PoPs? spread evenly globally?), how frequently files that can be cached are requested, the capacity of each PoP, the contention of each PoP, etc.

A few years ago when the customer and traffic growth rate exceeded the network expansion rate the answer was probably "not big enough", but we've since upgraded almost every PoP and added a huge number of new ones: https://www.cloudflare.com/network-map/

The answer now is "more than big enough".

We cache as much as possible, for as long as possible. The more requested a file, the more likely it is to be in the cache even if you're on the Free plan. Lots of logic is applied to this, more than could fit in this reply.

But importantly; there's no difference in how much you can cache between the plans. Wherever it is possible, we make the Free plan have as much capability as the other plans.