Not sure what you mean by 'descretionary' (I understand what you're referring to)... there is no such thing as successful/real active trading that doesn't involve high objectivity, which means it may be coded to a large/all extent, even for 'non-HFT' ...unfortunately being a trader today means having CS skill, which is a drag, but will rule you out of any hope of a 'real' finance job, be it at a prop firm like DRW or your own firm. If you can't code, you won't be a successful trader. Proper execution is a third of the job, and on most days, is all of your job. Managing code externally and running your economic logic that way, while leaving the tedious order executions to a properly written and deployed script is how trading today is done professionally, fwiw.
Many prop firms will demand experience or some nice academic affiliation. Job offers are scarce outside of December-May recruiting to my best knowledge.
It's great to be interested in this but know the limits of being a professional and wasting your time. I was a 'nonprofessional' while younger with just an interest, but became involved for completely separate reasons (because it was one of few good career paths that fit both my values while also being 'real' 'immediately possible' and 'tried and true'...since that point, nothing glamorous at all....in fact, it was to the contrary!)
Side note - majority of 'stuff' on ET is in the larger category for better or for worse...inject a little hotshot-expert provocations and also odd egos, and ET is more of a hotbed for comedy than legitimate trading. All of the good outlets for finance messaging are largely useless if you do not have networking connections or work for a large bank. Just saying!