It's legit, by the main Pixelfed dev. You can go to https://pixelfed.social and coil the Mobile Apps link and it goes to Pixelfed.org. There is also a sha256 checksum and download link at https://github.com/pixelfed/mobile-app

You can try pixel droid

Pixel droid on FDroid

i mean further down on that page shows other apps, one of which is pixeldroid, which seems like the other one you mention? it also lists fedilab, which i have (but don't really use lol)

while the size does seem large, perhaps they just haven't gone through the process of getting on the stores just yet? could be new and in progress?

Does the mobile site work better for anyone? The official app felt buggy last I tried

he doesnt want to make it oss until the first release. he said he will 1.0

fedilab is what i use

You could try either Moshidon or Megalodon, both of which work well with Pixelfed & available on the Playstore..