Running both rn with the same magnitude of mau and piefed is using significantly fewer resources. Unless you expect 100s of mau's I say ignore the concerns about piefed's scalability.

As for apps, those are more or less in the pipeline, piefed didn't have an API at all until a while ago and it's just now getting to a point where it's reasonable for developers to implement it. Voyager recently added Piefed support and iirc Photon also works with Piefed.

I would also recommend lemmy. It's more established, has a strong community footing. And above all, it seems to be well written (in terms of code) and has tons of clients (UIs/apps). And like the other comment says, I'm not convinced about the performance of piefed

A comment I came across like two weeks ago puts it quite well:

I haven't used piefed myself but I wouldn't want to switch to it because I feel like it gives more power to downvotes and karma (or "reputation" as they call it):

• Comments with -10 score are collapsed by default.
• People who get downvoted a lot end up with a ‘low reputation’ indicator next to their name. You’ll know it when you see it.
• Upvotes in meme communities do not add to reputation.

Those are three of the twelve points listed as differences to lemmy on their features page.

I also don't agree with some of the points in their article on "PieFed features for growing healthy communities".

from: https://sopuli.xyz/comment/17119490
the comments' thread is also quite interesting

Plus it's written in Python and has only a few hundred MAUs, so we can only guess how well it scales

EDIT: Regarding Lemmy frontends, I suggest you take at how the instance I'm on handles it. They append a single char in front of the url to signify the various frontends