Currently, iClone does not use RTX features. It also only supports one GPU. It will be happy with 24 GB of VRAM of the Titan RTX. Of course, this may change in the frture.
There is an Iray plugin for iClone, which is marginally useful for rendering animation. Although there are Iray versions that support RTX, the iClone plugin does not. It will support multiple GPUs.
Upcoming improvements of the iClone native renderer are expected to help close the gap between the visual quality of ray-tracing and iClone's own renderer. With effort, much can already be accomplished today.
Since you are specking your system apparently, it is recommended to have a data drive different from your system drive. Better quality comes with larger file sizes for content, so that is something to keep in mind. I have just upgraded my system drive to 1 TB, and I have a data drive just for RL content of 2 TB. I have been around a while so I have a lot...