Stop loss is very important in trading because that feature will be reduce the loss and to minimize the risk. And percentase of stop loss should be less than take profit, for example stop loss 20% and take profit 35%. Stop loss very important in crypto trading because fluktuasion of crypto so high.
At the same time 20% move in a cryptocurrency price is not unusual and almost guarantees that your stop loss will be hit. Yes however it does limit your losses to the stop loss level.
It really depends on what coin you are looking at.
Bitcoin's fluctuations are not so strong compared to other altcoins, so if you trade at bitcoin 5%-10% stop loss could also do the work.
In order to use stop loss correctly you need to have some knowledge at trading, you need to find the right support level and to place the stop loss below that/close to that, so the stop loss will be enabled when you have an advantage over the market.
Usually placing stop loss without knowing exactly where you place it would do worse then good.