Aftering using online check in for my airline, am I all good to go?

I'm flying WOW air. I notice they have a 24 hour online check in, and it will give me my boarding pass immediately which I can store onto my iPhone via the Wallet app

I have one checked luggage and personal item, do I still need to have these serviced at a counter?

And what of my e-boarding pass, do I just give them my phone to scan it or do I need to print something out?

You sound good to go. You arrive at the airport, and if you are dropped off outside your terminal, you can check that large bag right there. Then you hear in, go thru security, find your gate (they tell you at legate check, but stay aware - Summertime's they us a change). You then eat, use the bathroom, and relax until boarding.

You are mostly ready to go.

When you arrive at the airport you will need to stop at one of the Self-Service Kiosks to print a Luggage Tag that will go on your checked bag. This is NOT your luggage tag with your name and address, this is the tag the airline uses to route your bag to the correct location. You can then go to the baggage drop and hand your bag over. Be sure to do this at least 45-60 minutes before(depending on the airport) or your bag may not make the flight.

After that you can head directly to Security and you will show them the Boarding Pass from your Phone. You don't need to print anything else out.

It was mentioned in another answer that you can use the Curbside Checkin(Skycap) service and drop your bags off outside the terminal. I do not think WOW provides this service, however if they do it may not be at all airports or at all hours. There's also most likely an additional charge for this service(generally a few bucks a bag). So you may find it just easier to take the bags inside yourself.