I am almost certain that one COULD configure Optane to cache the SSD, and I think it would have measurable benefits for some processor intensive applications in science and engineering where data sets <16 GB are being accessed 100s to millions of times in succession. but I don't think that the general user would notice an improvement for the OS and gaming.
However, for a budget oriented system, Optane is a great addition. You can purchase a 256GB SSD for the OS and core applicatons, and a 2-4 GB HDD accelerated by Optane. This allows you to get huge improvements in large games loaded on the HDD. I've done this for years, using a 32GB SSD to cache the HDD, and Optane will be better. It delivers most of the benefits of SSD for a fraction of the price.