if interface name is set as sfp-sfpplusX - it is capable of 1.25G and 10G, if only sfpplusX it is 10G only.
1. to achieve successful fiber link between CCR1036-8G-2S+ and CCR1036-12G-4S or any other SFP device you need to:
*) disable auto-negation and set interface speed to 1Gbps to routers on both sides.
*) re-plug module or disable/enable interface after these changes.
when this is done link should be active.
2. regarding lack of information "Tx Power" field I suspect that dmi information fetching from module failed. Reboot or power cycle should fix this state.