Here's my take.

1. I like the S bars better than the M. The S bars are still a good height, feel much more solid and weigh a bit less.

2. I’m not sure about this. As far as I’m aware of the only option that drops the cage for the pump mount is if you opt for the titanium model. But maybe that’s what you meant when you said “* M type (low weight)”.

3. Yes, the tire acts as the third contact point instead of the wheel on the mudguard.

4. Depends where you are doing this. The easy wheels glide over a smooth surface but if you were going to use them on anything more broken than sidewalk I would suggest using inline skate wheels. But honestly the easy wheels should handle 90% of your real world use. Easywheels are also pretty slim so it gives your heels a bit more room out back.

5. Drop it. This can easily be added later. Not sure of the weight but it is very light.