I'd like to double-check with you if we can use RJ-45 transceiver in Meraki MX250 WAN port? According to the datasheet it supports MA-SFP-1GB-TX - Cisco Meraki 1 GbE RJ45 Copper Module (1000BASE-T for twisted pair) for MX84, MX100, MX250, MX450. And MX250 comes with 2 x 10GbE SFP+ WAN interfaces (https://meraki.cisco.com/lib/pdf/meraki_datasheet_mx.pdf)
So do I understand correctly that 10Gb WAN interfaces should be also compatible with 1G transceivers like MA-SFP-1GB-TX, so they will be able to use RJ-45 in WAN port?