PieFed follows a similar format as Lemmy and Mbin. Those that are familiar with Lemmy will find it very similar, with some additional features including topic lists, optional private voting, new mod and admin tools, crosspost de-duplication, community wikis, etc. Thanks to how the fediverse works, you can use either lemmy.ca or piefed.ca to interact freely!
The true power of federation showing itself here. In this case, it's two software packages with the same server/admin team -- which basically future proofs both.
I'd make a recommendation: have some sort of cross-pollination tool. Basically, pull the database of all subscribed communities on Lemmy.ca and have a bot subscribe to the same on PieFed, and vice versa. Probably easy to do if you have server-side access.
Furthermore, in the ideal world, "Local" from the Lemmy instance includes the piefed.ca local commuities. This might be a harder ask. The reason would be to prevent bisecting the Local feeds.
Finally, ideally there is a community migration tool, to cross between Lemmy and PieFed if a community wants to move from one side to the other. This would be a bigger project, but would future proof Fedican even further should either piece of software become badly maintained.
Well, okay, I just created a year's worth of work for a programmer. How can I help?
You might be thinking of Mbin, the other one of the "big three" (more like big one and the other two). Mbin's biggest differentiating feature is microblog support. It's hard to boil PieFed down to one main feature compared to Lemmy/Mbin, but anonymous voting and de-duplication of reposts might be the main ones. However, its focus is still on the (Lemmy-style) threaded side of the fediverse.