Leverage is powerful and very useful in Forex Trading. With 100:1 leverage you are effective using $1 to hold $100 dollars. With 500:1 leverage will enable you to hold $500 using $1. This is nothing new to finance industry but widely use for currency trading in order to use the dollar unit value of currency.
It works with capital that funded the trade. The capital has to be in currency value or cash in order to attain the leverage holding. This is similar to derivative or contract for difference for stock and shares. Using cash to leverage is much more powerful than using physical assets as it is harder to dilute and cash it back. Therefore, leverage is still used by currency trade with capital at 100:1 leverage. This determined the 1 lot size of 100k contract in forex trading. (For mini lot is 0.1 lot of 100k contract).
1 lot actually holds 100k contract worth of currency. This is equivalent to $1k of capital used to hold $100k contract worth of currency. Since pip is used for currency movement, 100k for 1 pip movement will work out to $10 a pip. (10,000 pips actually gives 1 dollar, but in leverage context is $100k contract).
For trading account, which give 200:1 or 500:1 leverage is different from the currency trading leverage. Please do not mix up both. The currency leverage is fixed at 100:1 for currency trading of 100k contract. Mini lot is executed at 0.1 lot or 0.01 lot. For trading account leverage which is 200:1 or 500:1, this will determine your margin required to hold in order to perform the 1 lot of 100k contract. Using 100:1, is $1k. Using 200:1 is $500 per lot. Using 500:1 is $200 per lot. This of course with higher leverage you actually can buy more lots. With a trading account leverage of 500:1, you can buy 5 lots at a total of 1k capital.
No doubt this enables you to buy more lots with higher leverage, but the downsize is the drawdown and the pips loss still remains as per your trading lot of 100k contractions. So most money management software will use a mini lot at 0.1 lot or 0.01 lot to trade. ($1 and $0.1 per pip respectively). Therefore do not mix up these 2 . One is the 100k contract leverage for currency buy and sell which is fixed at 100:1. The other is your trading account leverage which is provided by your Forex broker.