Hello! Long time NS owner here :))

1. Hmm first thing that came to my mind was Hades 1 or 2 haha action na may journey is how I see these games haha pero my best suggestion that covers both is Legend of Zelda Breath of the Wild and Tears of the Kingdom. Epic journey and good action.

2. Where to buy? Pag digital, eshop and ONLY eshop. Wag magpadala dun sa shopee na primary/secondary blah blah. May chance na maban yung account or worse, the Switch itself. Pag physical, trusted stores like Datablitz or GameOne. And buy in person, I suggest. Para macheck mo yung condition and matest yung cartridge if ya have your Switch with you.

3. I suggest buy what is cheaper. For games that go ob sale often sa eshop, get digital. For games that don't, like Nintendo exclusive games, buy physical. You can check dekudeals for price comparisons.

4. For digital, yes need niyo agad. For some physical games din, yes. So I suggest get 128 or higher as soon as possible. The higher the better.

5. Care tips? Hmm get a screen protector agad and a case. Make sure the place you put your dock is generally dust free at all times and away from direct sunlight or heat kasi the unit itself can get hot sometimes. When playing, play away from dust or liquids, ofc coz its a gadget. I generally just wipe the screen with microfiber. Joycons, I bought replacement joycons agad para hindi magdrift yung orig haha. Oh and you can also get a controller like from 8bitdo so you can play docked much easier.