Topic: eShop 2 for $100 split and DLC still works?

I’m looking at buying a some eShop gift cards and have a few questions.

Can I use eShop gift cards for Nintendo Online Membership?

When you do the 2 games for $100 deal on eShop, does it automatically load to your switch or give you a code? (I’m wondering if I could buy one game for me and put another on a different switch.)

Also wondering if a DLC on eShop still works if I buy a digital copy of a game I already have on cartridge. (Also, if it has to install the digital version, will it carry over my save data from the cartridge version)?

I’ve never bought from eShop so I don’t know. Thx.

@Rambler Okay thanks. Right now Costco has eShop GC's for 20% off, so I'm just trying to figure out the best way to go about it. I just got a Switch but have been collecting physical games the whole time. I realize now how annoying swapping the cards are with the janky game card cover thing.

I was thinking of possibly buying Mario Kart as digital (even though I have it physical) since it will be the most often game I want to switch to for variety so I can leave whatever the other game is in the card slot.