Tourist visa or conference/business visa for south-africa

I have been reading various posts about visa confusion and specially this one is pretty close to my issue. I will be traveling to South-Africa for less than 90 days to attend an open-source conference. The ticket amount would be refunded at the end of the conference. I do have a person's documentid (approved by commissioner of Oaths ) and an invitation letter from the person for the visit, but that would make it a tourist visit even though the person is from the organizing committee. I also have an official invitation from the conference organizers inviting me to the conference and they are working on having an organizer's documentid so it will all be official (for the conference visa).

I had visited vfs global's office in my home-town http://www.vfsglobal.com/southafrica/india/conference_visaapplication.html and they insist on not just the letter but also documentid of the person who signed them as shared above.

Here's a brief list of things I want to do which I guess would be good under the conference/business visa route but not under the tourist visa.

a. Get reimbursement for airfare from the organization after the event is over. (i.e. sponsored by them.)

b. Any expenses incurred I could write as business expense for taxation purposes.

c. I also would be doing amateur reportage of the event for some mainstream e-zines, press etc. in my own country to also cover some of the expenses/overheads which will happen during the trip.

d. Also would be looking for if any work-related opportunities (remote-work), remote short-term assignments etc. do arise.

So, in light of the above scenario, which visa should I go for - conference or the tourist visa would be good enough for doing the above. I would like to do everything above-board hence asking.