Tui to SdC is, in fact, a very easy walk. Only slight elevation, depending what your tour operator had planned.
Try the different pasteis de nata if possible!
You need a little bit of cash, maybe 20€ on hand, 50€ stuffed away, if card is not accepted (or isn't working). You can draw cash in bigger towns with cash machines of the corporate banks (Santander / Abanca / CaixaBank).
From Tui on there are enough Cafes and Bars to walk in and use their facilities, but don't be fooled, there are some parts that aren't well equipped. Almost every small town and hamlet will have a Bar, but you never know their opening hours.
I walked Porto->SdC in July last year and it was an amazing experience.
Wish you a real pleasant time on the Camino.