1. All class skills are magicka-based. Some work only in melee range and look more like physical attacks than spells (NB's Assassin's Blade or Veiled Strike, for example), but in the end they're all magic. So you'll be a hybrid whether you like it or not; it's theoretically possible to not use class skills at all, but it's counter-productive. ESO is a game of resource management, so the smart way is using all of them. At the moment pure stamina builds are weaker competitively than magic builds. With that said, a few skill lines use stamina: all weapons, Fighters Guild. You can mix and match and it's entirely possible to make a warrior-like character. My main is a heavy armor DK with only one long range skill on the hotbar and she plays very much like an in-your-face skull bashing machine.

2. I don't PvP, so my experience here is limited, but people who take it seriously run in well-coordinated groups. I think you should watch some videos on YouTube and see for yourself.