Unless this is some special setup and you really need onlynet=i2p, then better to avoid it. onlynet=i2p will instruct bitcoind to only connect to I2P peers. Is there a reason to avoid IPv4 peers? If yes, then keep it, but the problem with onlynet=i2p is that, since creating I2P addresses is much easier than creating IPv4 addresses, an attacker may have created a lot of them and your node may end up making all of its outbound connections to the attacker, making it more likely to be Sybiled.

You do not need the bitcoin-cli addnode step, bitcoind will do this automatically for you.