I think the risk parameters should not be set by a hard percentage point. I've heard this many times over the years, 'don't risk more than 2%'. But realistically speaking, I think it's best to take into account the trading style. For example, if a trader only takes 5 trades a year, then 2% does seem appropriate.
What about a trader that does 5 trades a day? or 10 trades a day? What if a trader went 0 for 10 on the day while risking 2% per trade? it doesn't quite make sense.
Also, some traders have a good risk to reward ratio but perhaps not so good of a win to loss ratio. In each case I think the percentage being risked needs to be adjusted to suit the strategy.
Just my opinion, but I don't believe in the 'one size fits all' view when it comes to percentage risked.
If you don't stay humble, the market will make you humble