Betz limit was discussed on:
Lift devices = downwind devices (IMHO) like yoyo, “Betz limit” being 4/27.
Drag devices = stationary devices (IMHO) = torque devices (IMHO) like Makani’s flygen, @dougselsam’s Superturbine tm, @Rodread’s Daisy, @PierreB’s Rotating Reel, also conventional wind turbine, and device with rope-drive like @Kitewinder’s Kiwee, Betz limit being 16/27.
But lift and drag devices can have the same efficiency per wing area, and crosswind flygen like Makani’s wing swept far more space than required. So in practice crosswind yoyo and flygen efficiency (and perhaps space use) can be similar.