EOIP is used over internet , not local network .
You are stuck with 1500 MTU so EoIP *must* fragment full-size packets. EoIP has a 42 byte overhead so you are fragmenting any packet over 1458 anyway.
If you are trying to shove a 9000byte jumbo frame down an EoIP packet you are going to process the fragment packets *7* times to fragment it into 1458 byte chunks.
Applying some math here, an rb951g can do about 81k pps, this fragmentation reduces that to 11.5k pps just by virtue of packet count
If you take the benchmark of 56.8k pps with firewall rules (estimating the fragmenting to be roughly equal to a firewall inspection) you'll be down to 8k pps. 8k packets * 1500 bytes = 11.44Mbps.
hope that math makes sense, but it's worse I think...
EoIP over WAN probably means ipsec encryption, because sending raw ethernet frames would be very insecure.
EoIP, fragmentation, and encryption, which eliminates any fast-path options, will pull you down to about 4Mbps.