Just as another point, there might have been a typo in one of python 1st reply.
The 2x4SFP is supported on EX4200 and EX3200, NOT on EX4300. This module does NOT support a mix of speeds. You must set PIC speed on this module to either 1G or 10G - no mix.
The 4x4SFP is one of the uplink modules supported on EX4300. This module supports 4 ports of 1/10 all active at same time. The question is whether Juniper does or does not support a mix of speeds (1/10) on this module. I know it can be done - been locally tested. The issue is to get this to work, after configuration a PIC reset was required to get active. There is no config method for this module at the PIC level to set the PIC speed, as mix could/should be available.