I think you lose access to all digital items purchased on the eshop when banned. So it can affect users regardless of if they have the subscription or not. It is quite serious.
Pros: Make backups of your physical games and play them digitally (or sail the 7 seas). Homebrew like emulators, ports. Game modding, overclocking, fps unlocking. You can even install Android, and Linux on a modded switch.
Cons: at risk of getting banned, possibly violating your warranty. Bricks are also possible if the mod is done incorrectly, but the chances are very low unless doing a hardmod.
I use a modded v1 switch currently, and I highly recommend it. Just make sure to make emunand as a designated sandbox for homebrew and hacking stuff.