Theck out the Track selector.
Most of the info you will want is there.
I totally agree with woodcote, a nice curve that tightens in the middle is fun and also makes for easier driving.
I have also used two 22.5° R1 set 180° to each other for a little "wiggle" in the track (cehck that your guide blade are short enough to manage this) or when the track just won't match up.
That is about the only time I would condone the use of R1s though....
On a tight layout I ounce did an R3 -> 22.5° R1 -> R2 curve. It worked but I held my breath each time I went through it.