The difference in applying for the two is basically that the Business visa requires an invitation letter. Given that you are only going to be there for a short conference, are presumably not high-profile enough or undertaking serious and prolonged busines negotiations, and are combining pleasure activities--I'd just go for the L tourist visa.

On the one-size-fits-all application form, you would not fill in an "inviter" but just put the name and address of the first hotel you'll be staying at. Under purpose, tick the "tourist" box and don't mention or indicate the conference box at all.

Do not worry about not telling the "whole truth" to the Chinese government. I assure you, they would have no hesitation in not telling you the whole truth, when it suits them. In your case, go with expediency rather than perfect accuracy.