Having more RAM doesn't increase memory bandwidth and having more memory bandwidth doesn't necessarily mean better performance. You aren't even able to make use of all of the bandwidth your M1 is capable of in the real world [1].

Apple Silicon has good perf/watt but the gap probably isn't as big as you're thinking.

[1] https://www.anandtech.com/show/17024/apple-m1-max-performanc...