to/from the router (and thus the internet) will be limited to 100mbit
Assuming of course that the uplink to the internet is 100M. And that the router with firewalls, tunnels, NAT and all can actually push whole 100M trough. That's a pretty safe assumption with 100M, but I've seen devices which technically hve a gigabit ethernet connection but with real world traffic the routers CPU is a bottleneck and it'll limit speeds well below that.
RB4011iGS+ I have can do (according to routerboard) up to 7Gbps for less than 200€. I've been pretty happy with it with my 1G fiber connection and it doesn't break a sweat while doing that. Granted, I don't run very complex stuff on the thing, but for me it can saturate the bandwidth I have available. From the ISP side I could go to 10G, but I don't have any hardware which could manage it, so I'm not interested (at least for now).
I initially had Edge Router X from Ubiquiti, but it stalled at around 700Mbps, so that thing is now glorified POE switch on my network and majority of the traffic goes trough mikrotik router and it's been rock solid since installation.