speaking of WABs, i saw an interesting take on them in Breath of Fire 3 for the playstation, where trees near the player path were 6- or 8-way quads (more like asterisks * from above), where trees more “in the forest”, ie, away from the edges, were the more traditional 4-way quads.
because of the mostly-isometric 3/4 view in this game, the high-quality trees mostly obscured the low-quality ones, while still keeping a low polygon count despite a high number of trees.
(on the billboarded sprites issue: anyone else used to strafe in cirles really fast around enemies in Doom just to watch them spin? that was cool. heh.)