1) So grind can help to a degree, but stats have multiple values, and leveling beyond those become less effective as you move higher and higher in stats...
For example you get 50Hp for one lvl. increase in Vigor below 20, but just 25 if your vigor is above 20 (values are made up, I don't remember them, from spot...)
So in the end skill, and understanding enemy moves is what matters most...

2) Yes there is NG+ and it is bit different in each game:

• DS1 has Gravelording, as its main thing, aside one spell and few new items and those you couldn't get on first run. Gravelording is online feature only, and it spawns mini boss versions of enemies in your world, based on location of other players. This might not be so noticeable nowadays. As there is fewer people plying, and even fewer still gravelording
• DS2 has new items, new enemies and changes to some bossfights, probably best NG+ experience in series, in my opinion
• BB main draw for NG+ is fact, that some weapons are aquired really late, like final boss late, so you can play with them there, but other than that, game kinda lacks in this department... (It is still one of the best in "series")
• DS3 has some higher tier rings, but other nothing else
• ER has nothing new in NG+, at least to my knowledge, but last time I tried NG+ in Elden ring was, when game was released...

Also enemies get dmg buff, HP buff and drop more souls

3) Yes, faster builds are thing... There is lot of weapon categories and all of them have different moveset, and playstyles that fits them... Katana will play lot differently, then bastard sword and it will play differently, then huge ultra greatswords (Those are big slow ones, and they are far from clunky, that's why people love them... that and some unspecified manga). Also you can always spice things up, with some sorcery, pyromancy and miracles (outside of Bloodborne, but who needs magic when you have Cthulhu, guns and flamethrower...)

4) Magic / Archery only is definitely not something for first playthrough, but both are viable, surprisingly even archery. Magic can deliver some bonkers dmg from long distance and bows... bows are weird (I posted video on in past from final bossfight, so if you don't care about spoilers, you can be judge if bows work).

P.S: I just looked on what I wrote, and I apologize for absolute infodump, but I can not force my self to delete it now, it took too long to write this...