Looking at the ANN, it shows that the final product isn't expected to be available until 2019. If there will only be Alpha and Beta testing in 2018, will you be paying the miners thaty are helping to test your software in the early stages?
CPU-based rendering is the old fashion way to compute things. CPU does most of the rendering, so cpu is basically important than gpu for rendering. Gpu rendering will nearly always be faster, but may make your windows feel laggy during rendering when you use your card as the display output (my experience).