Hi, I am traveling for business from US. I am a US citizen. My meeting is in Shenzhen but I am flying into Hong Kong. Is it best to fly into Guanddong to eliminate having to go through Hong Kong or do I have to get 2 visa (Hong Kong and China mainland)???

Also what is the easiest/most economic way to get from Hong Kong to Shenzhen?
And what is the most tourist attraction way??

traveling in November