RB2011 as modem on optical 1Gbit connection - max throughput

My provider issued me an RB2011 to use with an 1 Gbit optical connection. Because it can deliver no more than 300Mbit as a router, i was forced to buy a second router with hardware NAT, so the RB2011 will serve only as an optical modem.

Question: How do i set up the routerOS to achieve maximal throughput ? Essentially it must act as a dumb pipe between SFP-LAN2 ports.
I heard something about fast path and using it as a switch, but i have no experience with RouterOS.