Is 创业者 the best translation of entrepreneur as somebody who is trying to run a startup?
企業家 (T) or 企业家 (S) is the correct translation for "entrepreneur"
it doesn't indicate the size of  the business that person is running, ,  

For that, we have 大企業家 (T) or 大企业家 (S) meaning large profile entrepreneur)，and 小企業家 (T) or 小企业家 (S) meaning small profile entrepreneur.

For a start up business owner, the term is 新進企業家 (T) or 新进​​企业家 (S) meaning start up entrepreneur

創業 (T) or 创业 (S) means "to start a business" 

創業者 (T) or 创业者 (S) means " one who starts his or her own business" 



T: Traditional Chinese

S: Simplified Chinese