As discussed over in:
benchmarking VPNs is more subtle than one would want. If you say OpenVPN up to 500 Mbps you really should figure out what exact OpenVPN configuration you are interested in (it gets a bit simpler with wireguard, as wireguard in its current form does not offer many options to choose from).
But typically i would guess you need a x86 or a beefy arm CPU to achieve that throughput, given that you need a router in the first place that can actually do the normal routing/firewalling duties at that rate....