I like 10% or 15% nitro and all synthetic oil. For your 46 two stroke 10% nitro is plenty.
Most of the manufacturer's standard oil content is usually 18%, just stick with the mainstream fuel and it will be fine. There is no need to get too wrapped around the axle when picking out fuel. I like the all synthetic oil because is easier for me to clean off the plane than the castor oil is. I think the modern synthetics are just fine for most normal flying conditions. If you are afraid of not having any castor oil get the synthetic / castor blend, the castor is usually 5% of the total oil content. If less than 5% castor is offered I would get the lowest ratio available simply because the less castor in the fuel the easier it is to clean off the plane.
Once again don't drive yourself nuts agonizing over it, all of the Byron fuel is good stuff.
Actually when I buy fuel price plays a very big role in what I pick out and I don't spend extra for bragging rights when it comes to the fuel.