As for the scariness question, the bar here is inarguably Revenge of the Mummy. I know it's been twenty years (gulp), but that was aggressively marketed as a "psychological thrill ride" that would challenge many fears, ranging from darkness to death to insects. The ride itself, when you break it down, is also fairly intense in nature. You are sent to your doom on a cursed movie set, where your one ally has been bound before being basically executed by the antagonist in front of you. Imhotep, which it should be emphasized we mostly see only in gooey glory, threatens to kill us if we don't offer our souls. We are attacked by man-eating scarabs (although the evidence of their destruction has been sadly removed post-refurbishment) before Imhotep attempts to make good on his threat. From there, we are attacked by a variety of mummy warriors before another victim - a hapless ride attendant - is murdered gruesomely just out of view.