VLAN hopping is only possible due to misconfiguration. I'd like to be proven otherwise if that's not the case. VLANs are used EVERYWHERE where it matters. And no, the single port is absolutely not a bottleneck because the port is full-duplex.
If you're trying to push close to a gigabit up and down simultaneously that single port will become a bottleneck. I agree for most typical use cases it is not a concern.
Both get 500Mbit.
Bottleneck.