Firstly, I think you need to separate your question into two parts:
- Which currency should I hold my money in
- Which country should I hold my money in
If you are Chinese, live in China and intend to stay in China for most of your life then the default answer to question 1 should be Renminbi. Question 2 is not as important, you can hold USD in almost any country in the world.
Any investment you hold has risk, which may include market risk, credit risk, liquidity risk, inflation risk etc.
Holding USD will expose you to exchange rate fluctuations as well. If the Renminbi rises in value against the dollar your returns in USD will be reduced by the same amount (remember that for currency fluctuations you have to multiply the percentages, see here for a good explanation).
The first thing you probably want to do is find out exactly what the assets are in the 理财 you have invested in. The fact that there is a 'risk level' (even if it is only 2) would suggest to me that the fund is investing in some combination of bonds and stocks which means that your returns are not guaranteed and could make a loss.
Interest rates on deposit accounts are mandated by the government in China, and the current 12 month deposit rate on RMB is 3%. To earn over 3%, GEB must be investing your assets in something else (I'm guessing bonds). Bear in mind that 1.5 years is a very short amount of time in investments, so don't assume this return will continue! I'm afraid I've only been studying Chinese for a year, so I can't really help you much with the link you've sent through - you may want to check if there is any guaranteed minimum return, which can be the case in more complex structured products.
Ultimately you will need to pick an investment which you feel gives you the best combination of risk and return for your situation, there are a huge amount of options to choose between. The 4-5% you are earning right now is not a huge risk premium on the 3% you could earn in China from a time deposit, but in the current environment you may struggle to beat it without taking on more risk. Before considering that though - understand how much risk you already have with GEB.