A single 128 Gb.
Ill probably going mixed physical and digital. Ill buy the less expensive.
And for what I spend in space on wii U(where I went mostly digital), 150 (128+22 from the 32 Gb internal) seems to be enough, so, i think i wont need. But if I need, Ill trade for a 256 card, and using only it.

First, I'll wait till the onboard storage gets filled before putting an microsd cards,
and then I'll just upgrade phone's microsd card and use the old one on the Switch.

I don't foresee multiple cards from my side though.

I never needed multiple cards on my 3DS and it has a pretty good mix of retail and download only titles. I don't think I'll need more than one card. I might not even need one!

Yea, I have two retail games (Animal Crossing: New Leaf and NSMB2 along with a shitload of 3DSWare games.  I'm not even close to filling up half of the 32 GB card.  Retail games can fill up the card quick but if you stick with mainly just indie and VC games you will never fill it up.  I use a 2 GB SD card on my Wii for VC and Wiiware games and it still has tons of space.  That probably is mainly because Wiiware titles had file limitations put on them by Nintendo (which caused a few indie games to skip WiiWare) and VC games barely take up a few MB.

i would buy mostly physical... so probably a 64 gb would be enought for indie games and save files

I prefer physical media, 1 for collectibility and 2nd because (hopefully like the 3ds) cartridges are hot-swappable. I think I will only get a 128GB SD card (should be enough for me) and just forget that it exists!

Possibly. All depends on how much my wife likes the system. If the answer is "A lot" then we may end up having 2 and she much prefers online distribution for content.