So in my NG+ I've just finished the first Palace. I'm playing on Hard, not using overpowered Personas and focusing in filling the spots I left empty in the compendium.
And, after doing again the first dungeon, I can't help but have this impression: I think that pressing R1 and moving between Safe Rooms wasn't implemented until much later in the development.
The dungeon is full of shortcuts, and there are various locked doors that can be opened in order to get faster to the dungeon. Furthermore, the game talks about "securing a route". It'd make much more sense if the Safe Room thing wasn't available and you actually needed to discover the shortest way possible to the Treasure.
The 99% change is... well, completely useless if you pop up in a Treasure Room that's an empty corridot away to the Treasure. The item that reduces the Security Level only feels truly useful here too. And the soundtrack change for 20 seconds of running feels a bit strange.
Lyn's vocal range probably doesn't go that high. They probably had to change the key to something a few steps lower in order for her to sing it comfortably.
I liked both version to be honest.
See also: the instrumental version of Last Surprise used in the PV#2 trailer was also in a higher key that they lowered for the vocal version.
They should have hired Lady Gaga then :/