I've used screws for past jobs.
See here
www.diynot.com/diy/threads/screws-for-cladding.596283/#post-5292688 , but J&N down the bottom of that thread does mention nails/pins, but I don't think he's posted for a while to clarify.
I would use suitable screws. I can't recommend a nailer, but I would want to trust the opinion of someone who does, someone experienced who has done so for many years and many jobs, as the wrong choice can cause problems - splitting, sunk heads, positioning, visible dips in the toungue.
There is a high risk of damage to the boards with hand nailing.
You won't normally have a problem with fixing through the tongue with the standard 18mm T&G boards. It's the thinner shed profiles that easily split. But splitting can occur due to mispositioning or poor machining/grain.
Likewise for warping. You don't need to mess about with spacers, as expansion gap is built into the groove rebate. However coating the back as well as the front of the board before fixing prevents uneven moisture absorption and evaporation and the higher risk of cupping and bowing.
Face fixing gives a completely different look, and face fixed nails look terrible IMO.