What type of methylcellulose would be appropriate for gel noodles?
There's actually a commercial product designed for the purpose - methocel for gluten replacement can be used to make noodles.

http://www.dow.com/dowwolff/en/food_nutrition/products/gluten_replacer.htm

It would be hard to specify a grade comparable to the agar solution - the two things do not behave similarly when hot and cold. An agar solution giving a particular gel strength will have a much lower viscosity when liquified than a methocel gel of comparable strength. And there are several types of agar - it is a natural product, its properties depend on the seaweed species, locality and processing method.

Experimenting with solutions of E50 would probably get you there, but I'm not sure that the Schellhoss recipe tells the whole story. The combination of seaweed gel with parmesan makes me suspect that the gel is acting as a MSG enhancer on the high natural MSG content of the parmesan.

Whatever, hope these ramblings help your decision.