Just borrowed a JCM900 head and Marshall 4x12 cab to record some death metal. This is the first time I use one of these and I don't wanna blow it up. I know you can switch between 100W and 50W, so I wanna use the latter since I don't need so much power. As far as connecting the cab, there are two inputs...one that says 4ohm input and another that reads 16ohm input. Which do I use?

I just borrowed a Marshall JCM900 head with 4x12 cab to record some death metal guitars and I want to add my Boss EQ pedal to the mix to alter the sound. Is it best to add the EQ through the effects loop or through the normal input? Any suggestions on how to set the EQ pedal and the amp EQ settings? Thanks!