Yes, Decipher is a genomic test on the most aggressive biopsy core. It gives you sn estimated risk of future metastases. It can usually be done quickly. Check out their website. Veracyte (the owners of the decipher test) has an Access Program that offers affordable rates for patients whose health insurance does not cover it.

If I understood you correctly, they will do RT+ADT shortly after surgery. After that, there are no further salvage options, so the point that you can always do RT after RP, but not vice-versa, is moot imho. I would definitely talk to a radiologist. For aggressive cancer they will likely suggest the inclusion of a brachytherapy boost, that is a high dose internal targeted radiation of the prostate. By my reading of the literature it is almost as effective as RP and has far fewer side effects that RP+RT in short order. The internal lesions need years to fully heal and putting radiation on top after a few months can result in permanent incontinence and guaranteed impotence.