If I’ve interpreted that book correctly then a strategy with a low risk/high reward is expensive and should be avoided.
To make my point, with a toss of a coin you are 50% likely to get heads but the odds of getting 5 heads in a row is 31/1, yet if you were trading a strategy with a r/r of 1:5, you would only be getting odds of 5/1.
You’ve to determine the win ratio an R/R for your system and then calculate the expectation based on a formula. There’s some variations but I tend to teach this one:
E = W% * Reward Avg. - L% * Risk Avg.
Make a matrix in Excel and you’ve got all the possible outputs traced.