Well, the experience is otherwise, more nitro makes an easier tuning of the enging because with a slight rich setting the engine is still performing strong and fast. With a low nitro content the window where in the engine performs well is smaller and if you do need power there is a risk you will go to lean.

The fuel consumption has also another but quite simple reason: there is less methanol inside the tank with more nitro, and you do need methanol for the combustion. You can calculate the avarage methanol needed per combustion, with more methanol (=less nitro) more combustions can be made, thats why some people are using less oil.

Changing timing by the length of the conrod is something no one (without tools and the right materials) can do, it is not the easiest way. Placing the cilinder lower or higher is much easier to do and is adviseable if you want to change timings without grinding, you can always go back.

More interesting is playing with the boring/stroke numbers. Long stroke will give more play in the hight of the ports, for sure with the exhaust. With a .21 square stroke it is 16.4mm, with a NR long stroke it is 16.8mm, you can make the exhaust poort 0.4 mm higher on a long stroke without affecting the combustion stroke. More port space and more rpm without loosing power (= combustion stroke)