We absolutely do not know anything about PC port. It could be great, it could be the worst thing ever.
Chances are 50-50. For sure it's a different engine than Dark Souls 2, so the fact it was good is really no guarantee of what happens with DS3.
We just don't know/can't guess.
B-Genius said PC is the lead platform, so it should be decent. It doesn't guarantee many options and stuff like that, but at least it should run decently. Minimum requirements are also not demanding at all.
Could have been a way to lock out players from wandering too far.
That would be amazing, but I don't think I'll hold too much hope for that, so I won't end up disappointed once again. Highly doubt they'd make cutscenes just for this preview build.
We'll see when the japanese version comes out, I guess. I wanted to stay the hell away from more Dark Souls III info, but now I need to know this. Will closely follow the import thread, if there is one.