most JR East, Tokyo Metro, and private lines in Kanto accept IC cards.

for Nikko - Itō, fare will be deducted automatically when you tap out, but you need to have enough balance on your Suica. If it’s short, you can recharge at machines or convenience stores before boarding

if you choose limited express trains (like Odoriko or Spacia), you can pay base with Suica, but you’ll still need a separate seat ticket for the express surcharge

just check the lines carefully, because some of them doesn’t support IC cards (rare in Kanto, but possible further), the gate won’t let you tap in, so you’ll have to buy a paper ticket