Finding Article Template for New Journal - PRX Quantum
I suggest you use the prx option included in REVTeX-4.2, e.g. using
\documentclass[prx,twocolumn,english,superscriptaddress,floatfix,longbibliography]{revtex4-2} (Without having compared too closely, the style used by PRX Quantum seems to be the same as in PRX.) If you have an earlier version of REVTeX that doesn't support prx, just use the preset for another APS journal. Either way, they'll handle the minutiae of formatting should the manuscript be accepted.
It's not inappropriate to ask journal staff about templates, but they state that submissions in REVTeX or MS Word are preferred, and I think using prx is the closest you can get using REVTeX at the moment.