What is it you want to do?
If you just want to follow PixelFed accounts, or you want PixelFed accounts to be able to follow you, you can do that already from your current Mastodon account.
You don't really need multiple accounts on here, because servers and server types talk to each other.
If you want to try out PixelFed, just sign up on a server. Each server is independent, so the account only lets you sign in on that particular server.
There's currently no way to transfer PixelFed accounts from one server to another.
The PixelFed app for iPhone is currently in beta testing (more info at https://mstdn.social/@feditips/109139292506397574)