So, Alby is the only extension I am aware of that combines a wallet and Nostr signer into a single extension. Coinos' wallet would not combine into a single extension with nos2x signer, for instance.

As for using Alby Hub, if you downloaded it on Windows, you are effectively running a Lightning Node on your PC, which means you must keep that PC always online, especially if you want to connect to it from other devices.

Without seeing exactly what the fee was for, it is hard for me to determine whether it would be a repeat payment or one-time-only. There is always going to be an on-chain fee to open a Lightning channel, and one to close it. However, when you buy channels in Alby Hub, there can also be a monthly fee, since you are asking the liquidity provider to lock up their own funds into a channel with you. Not sure which of these categories the 20k sats you were going to be charged is falling into. nostr:npub1xv8mzscll8vvy5rsdw7dcqtd2j268a6yupr6gzqh86f2ulhy9kkqmclk3x or others from nostr:npub1getal6ykt05fsz5nqu4uld09nfj3y3qxmv8crys4aeut53unfvlqr80nfm may be able to shed some light on that for you.

If you plan to go the self-custody Lightning route using Alby Hub. It is probably a good idea to learn about running a Lightning node, how to choose good channel partners, and how to manage your inbound and outbound liquidity. If all of this is sounding foreign to you, and you just want a wallet for zapping a few sats now and then, I highly recommend sticking with Coinos for now.