At least from what I have tested, 100 Mbps with reasonable latency over OpenVPN puts you into the x86_64 with AES-NI class of devices.
I haven't tested the Lantiq SoC, but I would imagine that there'd be a lot of complaints if it couldn't route/NAT 100 Mbps. mps' post confirms that it can't come close to 100 Mbps for OpenVPN and suggests that it may not hit 100 Mbps for WireGuard. Since it seems you've got routing/NAT and wireless, something to do the VPN. This assumes your device can route 2x = 200 Mbps, as packets will come in from LAN, out to VPN engine, back from VPN engine, then out Internet.
The Raspberry Pi devices are marginal for Ethernet bandwidth due to some design choices made prior to the "4" series, but should be sufficient for these speeds. I have not tested their OpenVPN speed, so can't comment if they are sufficient.