From what I have gathered, FX traders typically make significant money by trading with a large account size and/or utilizing leverage. How much and/or by how quickly those account sizes grow can vary, as some traders may even take on investor money once they really know what they are doing and have proven themselves.
Leverage can be used to magnify returns, but the other use for it is to limit risk and free up capital. Obviously, with leverage, you take on risk, but the idea is that you do not have to risk as much of your account balance as you normally would for the same size trade, whatever that amount may be. So, if you wanted to open a 100k position, for example, then instead of risking 10% of your account balance to do so (assuming you had $1 million to trade with), you could risk a small fraction of your account balance to open the same size position by utilizing leverage, therefore, limiting what you could potentially lose, while also allowing you to free up money for other trades.
Once your account grows in size, then you may not feel the need to use leverage anymore, as you may be able to make decent returns without it. Risk is subjective. What you may consider as high-risk may not be for someone else. You may think that 1% of total balance per trade is the maximum that you are willing to risk, while someone else may be okay with risking 10% or more per trade. You have to learn what works well for you and your trading style; do not adhere to some rule unless it makes sense for you.
You mentioned day trading. I suspect that many day traders may adapt their trading style over time, by eventually gravitating toward higher time-frames, since they no longer have to grind so much in order to grow their account and make really nice returns. Not all day traders do this, but some do. Trading on higher time-frames allows you to see bigger returns per trade than you would normally see if you were day trading, but it /can/ take longer to realize those returns.
Some traders that are just starting out (or starting over) generally try to grow their account quickly, so they gravitate toward the smaller time frames. It can carry more risk, but it can expedite things for some. Not all traders start with day trading, though. The higher time frames carry more significance with regard to market direction, support and resistance etc., and may be considered less risky as a result, so some traders may prefer that, especially if they do not have time to monitor their trades constantly. Some seasoned traders may even say that the smaller time frames are only traded by newbies, but I know that there are some very successful, seasoned traders that still prefer to day trade on the smaller time frames (but they also know what they are doing).
You mentioned compounding. Compounding can be very powerful, but it is also important that you learn money management early on. Part of that might entail pulling a percentage of funds out, periodically, and setting that money aside or investing it elsewhere…especially if you are not utilizing a large percentage of your account balance to trade with. Not only would this allow you to put that idle money to use, but it would limit your exposure to potential risk, in the off-chance that your broker decided to bail. Simply put, have a good plan…even if you are using play money and treating this more as a hobby; it is better to establish good habits and proper money management. Similarly, if you are trading on a demo account, always trade as if you were trading with real money and treat every trade seriously so that you are able to condition yourself and your thinking.