The grotto is just a mystery award I believe. I had a very nice Playboy for awhile and really liked it. Deep is defiantly not the word I would use to describe it. To me it had more of an old school with not many goals type feel....but fun to play even without the deep rules.
The centerfold multiball rules were pretty fun on how you had to hit certain shots and follow them up in a certain amount of time, and keep all 3 balls in play to get the various double and triple jackpots.
If Mansion Mania is considered a wizard mode it is easily the easiest wizard mode to get to of any pin I have seen.....though I always wondered if the 4th Mansion Mania was somehow different since it's insert is a different color. Or what happens after the 4th Mansion Mania. Another thing I never did do was to get all 12 Playmates recollected during Mansion Mania...I always wondered if it would light the next Mansion Mania insert for doing that.