Oil Viscosity after modifications

I think my concern may partly come from an assumption that a multi-grade oil performs better throughout its range if the range is smaller.

So for example a 20W50 performs better over its range than a 10W60 would. I have been trying to answer this question via google for about a week. I have learned a lot, but not the answer to that question.

Wow, perfect timing for this post. I used Motul 300V last year, 15-50 because I heard all the good things about it. Now this year I have also read that the Motul 300V is not good for cruising just for racing. WTF, they were going on and on about how Motul 300 cannot handle the heat of cruising and all the idling that happens at red lights etc. How can a "racing" oil not be able to handle that kind of riding? Anyway, so about to do my oil change before putting my bike on the road and was still thinking about Motul 300V, should I change to Motul 7100? This all seems so counter-intuitive. Any thoughts are greatly appreciated.