This question looks to be quite subjective, so here's my subjective view:
2% is probably too high for beginner traders that don't know how their strategy performs or have a trading plan. Also 2% doesn't suit all trading styles such as scalping, so it's not a one size fits all approach.
I trade intraday, set and forget on the stops, they do not move, I don't stop out early either or move to BE, I only move my targets in if the trades are going beyond a day.
So I've taken some inspiration from Maza and an article he posted about a combined fixed ratio/fixed fractional approach, to make the most of this approach you need to know how the strategy performs over time, such as max drawdown, margin requirements, max number of trades and so on, from there you can work out max percentage.
For me max percentage is around 2.5% per trade, at that level if I have max trades on at any one time I know that I would be risking no more than 30% of the account across all trades with it's associated margin requirement and max drawdown of my strategy is around 800 pips, combining max trades/max margin and max drawdown I know I'll never have a drawdown of more than approx 50% of the account, this combined scenario is rare, I'm happy with this approach as even with this scenario I know what the average monthly profit is over time.
However I am taking it in 0.25% monthly increments to reach 2.5% and I'm currently at 1.75%, as I need to be comfortable with each increased risk level, otherwise I know I would start to sweat if I went straight to 2.5% and ended up with the aforementioned scenario right off the bat and sweat trading doesn't work for me
Mazas article:
Mazas Combined fixed fractional/fixed ratio Money Management
and one of the threads Maza has posted:
Maza thread