I mean, it'll help with a lot of fast teleports & accesses to certain locations, etc. I personally just loved questing when I was younger so I had a bunch done when I got serious about maxing, and it has certainly made the game a bit easier. I'd recommend getting a majority of main quests done if anything. As for the actual QPC, no, I don't even have it; I stopped around 198 because they were rush releasing so many to get to 200. I haven't really quested since and don't plan to until I'm maxed/new location content like Priff.