Attached is screen shot. What does it mean? What does it do? Which check boxes do I check?

What you have checked there is fine. Just means your CPU can do the rendering or your card...and the Optix Prime Acceleration is some kind of optimization thing. Not quite sure with that one ;). I have that one checked and I have no problems.

You can have only your gfx card checked if you only want it to do the rendering, but if you have too much in the scene for the memory on the card, your CPU can't then take over the job.

Laurie

The two sections are for the two different modes of the render engine: PhotoReal or Interactive. Unless you have changed it you are likely using PhotoReal as it is the default, so the Interactive doesn't much matter. However, what it means is: you are telling the render engine what devices to use in each mode. GPU is the best option, CPU and GPU is a secondary option allowing the renderer to use both the GPU and CPU to render (I don't recommend CPU and GPU, there are many mixed reports of its stability and efficacy; your mileage may vary). OptiX is a ray tracer enhancement and it is highly recommended.

Checking both means that both will be used. Note that Interactive is for Interactive mode, usually used in the viewport, though you can also use Interactive mode for rendering, it is not the normal way to do things.

Optix is, as SickleYield puts it, "the magic go faster button." It should be on unless you are using certain AMD/ATI graphic cards, on your CPU render, because for some reason it is slower with some of those cards even though they do not contribute to the render engine.

In general, you should check all available devices for best speed, though on scenes with really short render times, loading the scene onto your cards may actually take longer than the render itself. (Usually the exception, not the rule.)

The build of Iray in DS 4.9 eliminates the occasional crash caused by some content with both CPU and Graphics Card checked.

If I choose to upgrade to 4.9(if rendering really is significantly faster enough to make it worth my while)will I have to uninstall 4.8 to do that or will it install over 4.8?

I just spent a whole lot of time recently installing 4.8 and reinstalling ALL my Victoria content & spending several days unzipping content to My Library. Will I have to do that all over again?

The only thing I had to do was the Database export, as a precaution. The installing of 4.9 takes care of the other things you mentioned.

You might want to hold off a bit longer on 4.9 as a "Hot Fix" to 4.9 is in beta.

"Database export." How is that done?