While Schoolbook is probably still a variant worth playing, when H.G. Muller gave us a free Capablanca Chess engine with decent strength, I discovered that the game is unbalanced in favor of White because of 1. c4! I spent weeks trying to find a decent Black reply to that opening move without success. I have put Schoolbook on the shelf until someone finds better defenses for Black.
Before I gave up chess variants, my research showed that the Modern Carrera opening setup: RANBQKBNMR, where “A” is the Knight + Bishop Faerie piece and “M” is the Rook + Knight Faerie piece appears to be more balanced. Of course, there may not be a Capa opening setup without a big advantage for White on account of how much power is on the board. Carrera Chess has been around almost as long as Chess itself (Carrera, Bird, Capablanca, Grand Chess on a 10x10 board, Gothic, and most recently Seirawan Chess on the 8x8 board) and has never caught on...but, quite frankly, that’s true of pretty much any western Chess variant with the possible exception of Bughouse Chess.
For people who wish to play Modern Carrera Chess, I have both a Zillions rules file (Zillions of Games needed to play; this program is a $25 purchase and worth every penny) and a ChessV setup file (ChessV required to play; free download).