Thanks to Stolistic for these pictures, attached for reference are pictures of an IGT Player's Edge Plus (PE+) Regular/standard MPU board, Superboard MPU board, and a Wingboard daughterboard PCB.
Either the regular/standard or Superboard MPU board may be used in a PE+ machine.
Note that the Superboard has an additional EPROM socket next to the "PROGRAM" socket labeled as "DATA". The presence of a DATA socket on the MPU makes it a Superboard. The lack of a DATA socket makes it a regular/standard MPU board.
The Wingboard is a hard-to-find optional add-on daughterboard to the Superboard which allows the user to choose five video poker games (from a list of supported games - not every video poker game created for the PE+ is supported) to make their own Multi-Poker game set.
Top picture, regular/standard board. Second picture, Superboard. Bottom picture, Wingboard.