Tun devices are possible and useful on exe.dev today, because it means, for example, you can install the full copy of Tailscale.

But to your point: if a single VPS meets all your needs and you do not feel constrained by the marginal cost of another VPS then the exe pricing model is not going to bring you much value. Perhaps the automatic TLS termination and auth proxy with link sharing is useful. But if not, then it sounds like you are well served by existing products.