Would it be beneficial enough for say a 5k? Maybe doing 40-50mpw of all easy runs (one long run).
Yes. Although it also depends.
If you've been training hard for a while, and you've hit lots of 50 mile weeks over the years with quality, you won't get faster.
If you are new to the sport and you have not run that mileage before, you will most likely get faster. Although if you run 50 mpw for a few months you won't necessarily set a PR in your first 5k race. Run a few over the course of 4-6 weeks though, and you might be surprised at how much time you can drop.
I think the best you could do would be to run as much easy mileage as you can/as you enjoy. Once every week or two run a tempo or progression run. A few times every week or two add some strides or hill sprints.
Note, those could all still be "easy." At the point that your tempo run becomes a slog and you are straining to get it done, stop. If you're running strides or hills and you start straining and dreading the next rep, well, you should have stopped one or two reps ago.
Train don't strain. Run fast and relaxed. And don't limit yourself to 50 mpw. If you're running well and enjoying the process, keep going.