As a designer, even for digital work (so long as it’s not animation), a physical portfolio is still the expected requirement. The best way to present work to clients in person is still images printed and matted in a physical portfolio. An online website portfolio is an absolute requirement as well, but you’re expected to have a matted presentation in person.
Personally I could not imagine using any tablet display, as it’s too small for one thing, and for another I’d be worried about glare, range of visibility, and then handing it off to a client to look closer at and them being unfamiliar with the controls. Or worse, the dreaded “as you hand it off they touch the section of the screen that accidentally closes what you were looking at”. It simply makes for a poor presentation and makes it look like you’re tripping all over yourself. A physical matted piece will work every time with no issue, guaranteed. Well, unless the client tries to use it as a coffee coaster, anyway.
ETA: If this is a “meet at a coffee shop” client, a physical portfolio is a bit overkill. I’m talking, you have been invited to their office and are being considered for a position. Then you need a physical portfolio.