As far as other dissos go I've mixed it with ketamine, 3-HO-PCP, 3-HO-PCE, nitrous, salvia, and 2F-DCK before. Mixing it with ketamine barely noticeably changed the experience so I deemed it kind of boring compared to either on their own, where their unique character has more of a chance to shine imo.
Very doubtful anyone has r-isomer-only ketamine. For clarity, the "r" there stands for "rectus" not "racemic". Racemic is the mostly commonly encountered ketamine by far, and unless you have access to pharmaceutical Esketamine, I would be dubious of people's claims they have s-ketamine. Lots of dealers claim their shit is s-ketamine, b/c that's the popular buzzword right now in that world.
It's also somewhat possible the 3-fluoro-2'-oxo-PCE is in fact 2-fluoro-2'oxo-CE, not that it matter much. Sauce to follow: