You running OpenVPN or Wireguard? . From a speed loss point of view Wireguard poops all over OpenVPN.
The M1 is cat 16 hence probably why the faster LTE speeds.
Luckily for my meagre mobile bandwidth needs reliability, easy of use and flexibility are more important to me then outright speed so the Mudi suits my requirements.
In “ideal” locations and conditions like CBD on average I can pull around 35Mbps on the Mudi on Cat 6 and my phone can pull 100Mbps+
On the small cell at the holiday home I probably only get between 9-12Mbps on either device but it’s enough to stream some 1080p and surf the Web 
If pure speed was available on my phone and not the Mudi and I really needed the speed I’d probably just USB tether my phone when required
Don’t forget too there’s so many other factors that will affect speed like congestion on the towers, distance to towers etc. 