Perception vs Investigation - i agree this is an area where there is a lot of "consult your gm" clarity needed. On this forum i have seen gms whose views are way off mine in this regard. Have sern it in streams as well. Have seen others more in line with mine.Yeah, it's the same issue, but I always like to remind everyone that the World of Darkness rules were entirely copied from Shadowrun. (Nothing against World of Darkness, just giving credit where it's due.)
On the one hand, yes, it's important to not get too caught up on the specifics so that you lose track of how the rules work as a whole. On the other hand, this is still a game, and you can't meaningfully play a game if the players don't understand the rules. One issue with how 5E works, where the DM can either lower the DC or give Advantage to the check, is that the players don't necessarily know which way it's going to be - and that detail can be incredibly important when they want to decide which action they're going to take.
The other big issue where ambiguity hurts 5E is in the difference between Perception and Investigation, because the things that they govern can be so similar in terms of what they look like, but the mechanical difference for any given character can easily be a ten-point swing. I would have preferred if they'd spent more effort on distinguishing between them, and less effort on calculating specific numeric modifiers.
(To its credit, the system does try to establish some general guidelines for both of those issues, but it can still be hard to make sure that the DM and the players are all on the same page.)
As for DC vs advantage, i think the do in the rules a better job there. But to be sure how i choose DCs is a session zero campaign charter thing for me. I think itsvimportant to know that for players to have their characters make good informed choices.
As for WoD vs Shadowrun... I may have had it wrong then. I had thought SR 1 had variable dice in pool **and** variable successes required but thought (mistakenly) it had a set threshold for what a success was. Then again, now that you mention it, i think i recall armor ratings of like 2-6 or so... So likely my bad.
I knew VtM had all three in play and (while playing many many games and loads of fun) laughing at the math fails.
Then again, it was 2nd or 3rd i think, when they locked threshold at 7 (since they could sell special dice.)