My node almost ready

I'm syncing bitcoin chain and almost there. I went with MyNode for the simplicity but now I think I should have gone with raspiblitz.

Few questions:

1. If I decide to flash raspiblitz instead, does that mean I have to sync blockchain again, or is the SSD data valid as it is?
2. After this I want to connect my watch only wallets (sparrow, blue wallet, green wallet) to my node directly. Where can I learn how to do that?
3. I wanna start using lightning network as well, but that seems challenging. Can anyone outline what kind of setup for lightning I need on my node, and how to connect to it and keep channels open, all that stuff?
   I don't mind if there is work involved, but I want to know all the details.

Thanks.