A bandwidth of 6 Megabits/second is commonly considered sufficient for a good user experience. Any half-decent internet connection will meet this requirement. Slower connections may also work fine, but it's important to point out that much slower connections will negatively impact your user experience. Remote operations will take much more time to complete and operations that are more data intensive, like VNC, may not even work at all.
Some SIM cards, mainly M2M or IoT SIM cards, have a very limited bandwidth which is insufficient for a VPN connection to work. Read the provider's fine print for remarks about limited bandwidth and avoid those SIM cards.