Can I safely trim civicrm_job_log and civicrm_log?
I think you can safely trim the civicrm_job_log, only the latest entries are probably useful (and given how little information the cronjobs return, I'd even doubt that ;)

As for the civicrm_log (or subscription history), it might be more risky to remove as you will loose "useful" history of what happened with your contacts, but from a technical point of view, it shouldn't be an issue, as long as you are ok losing that history.