8% sounds insane and unachievable, I mean China is basically around 30% of the world's economy. For them to grow that much while rest of the world is mostly suffering would require some sort of economical miracle. 4.3% is still massive and it sounds more realistic. But let's wait and see what happens.
The thing about making the RMB into the global reserve is that it is likely to hard cap the ability of China to accumulate real growth, because to do so, China must buy massively more than they sell, in order to spread the RMB.
Assuming global reserve will make China fully usurp America's role as global hegemon, but that doesn't mean much if it means the average people in China will see wages stagnate and that industries, jobs, will have to move out of China into other countries, making them dependent.
This is why China instead wants a basket of different currencies as reserve, so that they can still comprehensively play the mercantilism game.
Appreciation and/or depreciation of a currency greatly affects un-adjusted nominal GDP, hence this measure tells us even less than normal GDP, which is honestly also pretty bad. So I wouldn't even think too much about the appreciation rate of the Yuan.
Currency can fluctuate, but what gives real power is basically how much "stuff" you can produce. Stuff of course not only being goods but also research, educated workers etc. This is the metric that really affects living quality and ability of the country to withstand crisis.
China reached the status of largest economy by GDP not because it desparately prioritized acquiring GDP, but because they followed the path of growing productive forces, which naturally led to more GDP.
And most likely China will one day also assume the role of global reserve currency. But it should not be rushed, instead it should come naturally through developing the living standards, the industry, improving and increasing the jobs etc. This is the concept of Xiaokang society, where the "little man" or the class of commoners, are the ones whose needs are put first.