I'm looking at SD cards and trying to make a decision.  How important are read/write speeds on these cards?  It seems like it'd be worth it to buy a faster class of card, especially if you're going mostly digital.  However I also just became acquainted with how expensive some of these cards are.  I originally assumed I would be buying some massive card, but now I'm looking more in the 200+ GB range. 
I guess what I'm asking is, if a card has a r/w speed that's 2x faster than another card, would you expect to see digital games load twice as fast?  Do we know if there's a cap on the read speed of the SD card reader Nintendo went with?