1. They have some similarities. More "user-friendly" and fast-paced, less punishing, but with really cool mechanics like monster climbing, special skills bound to face button, etc. And the skills are all unique and interesting. Like a volley of arrows, dagger attack spam, setting yourself on fire and climbing the enemy, charging a greatsword attack, perfect blocking with an elemental shield + riposte to inflict an elemental status (e.g. freezing the enemy), creating a vortex that draws mobs in and damages them, and of course tons of badass magic spells.
2. Full open world, but much smaller than Skyrim. It has a few Souls-like dungeons too.
3. A lot, and yeah monsters eventually respawn so you can just re-visit previous areas and fight them again. Bitterblack Isle in particular has exactly the kind of monster-slaying loop you'd want.
4. Really good. You don't just gain XP, you also unlock skills related to your current vocation, and you can change vocation at any time (after completing an early story mission). Each vocation has 3 types of skill: active (the ones I described above, that you bind to face buttons), which are directly tied to your vocation, passive (called Augments) which can be shared among vocations, and "Core", which are shared among common weapon types. For example, a Core dagger skill is the dodge roll, a Core staff skill is Levitation; so any vocation where you can equip a dagger will let you dodge roll, and any vocation where you have a staff equipped will let you levitate. You can customize your character abilities like that, along with their gear of course. It also has the best character creator I've seen.
I'm playing on normal and it's smooth sailing.
