All that is important is your setups give you consistent results, good or bad. So you can determine what works and make adjustments. Trading in Rs helps with that. Consistent risk should help provide consistent results. So using a different size R for different setups is fine as long as it is consistent within the setup to analyse later.
I like the average profit divide by the sigma as a good indicator on the quality of the setup. Then use this table (from Van Tharpe Institute):