Support for the big English sides aside, which is obviously the majority, then in my experience the more northern ‘Gwent’ valleys towns (Rhymney, Tredegar, Ebbw etc) are overwhelmingly city. Some jacks to be fair, probably as it’s an easy enough drive to Swansea down the A465 but public transport is almost non existent.
I’ve never met a county fan or seen any paraphernalia in the area. Unless you were originally from Newport or had family links I dont know why you’d follow them as Cardiff is basically equidistant and with better transport links.
Know plenty that follow Merthyr to varying degrees too, including myself.