I believe you only need an unlocked bootloader.
TWRP2 has the 'dumlock' recovery method that 4EXT uses. So GooManager *should* flash the recovery just like 4EXT does (where no fastboot is needed). The no fastboot for kernels method was actually designed for TWRP2 first, and permission was given to 4EXT to use it, as well.
ROM Manager, the last I checked, did NOT do this 'dumlock' method and won't properly flash CWM on a S-ON device. So I would recommend staying away from ROM Manager (unless someone corrects me).
TWRP uses GooManager to install the recovery