How much does a vpn service performance depends on how new/advanced your device hardware is?
If you’re talking about small devices like routers, the hardware matters quite a bit. Also depends on the type of VPN client you’re running. For example openvpn is a lot more resource intensive than wireguard.
If you’re talking about full desktop or server CPUs, then most of them can easily handle the resource loads, and for a single VPN connection your main constraint will likely be your bandwidth.
Was talking about devices like iPhone (14) or iPads air (4th generation) am getting vastly different vpn performance from same wifi/vpn provider.
When talking about apple devices, there’s a lot of other things that might be coming into play. Apple is known for having some odd behavior with VPN clients and even creating DNS leaks. There’s not much more I can answer for you without knowing the specific types of devices, which VPN service/client, and how you’re using them (e.g. wifi vs mobile data, etc).
Both the devices you’ve listed have solid processing power, so I doubt your speed is being greatly affected by pure hardware constraints.