It's a private channel, so there's no routing. The way it works is the Phoenix app runs a node that connects only to the ACINQ node. You send them an on-chain transaction and they take it and open a channel to your app node for a larger amount and push the amout you sent to your side. That is the only channel you'll have, but you can splice in more sats if you need it using the same process.

All payments route through them and they handle all the lightning management stuff, but they also have a monopoly over all your transactions and can dictate whatever fees they want. Currently it's 0.4% plus 4 sats base fee so it's too expensive for zapping imo.

I guess for now it makes sense, but I bet they'll have some policy about it in the future. I can't imagine it's sustainable to provide an extra 75% liquidity on every channel.