Actually you can still play online and cheat at the same time
Also FFE is using offline data to go online so if you cheat your damage and items while in offline you can also use it when playing online
btw this is guide that i found for ppl who need
http://www.elotrolado.net/hilo_ho-tuto-instalar-cfw-rxmode-compatible-con-emunand-9-6-classic-mode_2081946