Recently there have been two more PieFed instances created, which offer accounts to anyone who wants one:
Feddit.online is hosted in USA which should make it a little faster for people there. It also has a different topic structure at https://feddit.online/topics than PieFed.social has.
So someone like me that has a couple hundred subscriptions is a far bigger server load that someone who browses via all?
Yeah, sort of. The total number of subscriptions (by all users) determines the load caused by federation. If you subscribe to 200 communities then I subscribe to the same 200 the federation load will not increase.
So once an instance has more than a dozen users pretty much every community that exists will be subscribed to and adding more users will not increase federation load (but it would increase load caused by the UI)