Hi I'm a Nonbinary nerd and I'm really knew to the doing but not the concept. I do have one question, the game I want to run's Remaster/HD version is in the listings but not the original. Would I want to add the new version as a Sub game or new listing? (Game: Might and Magic: Clash of Heroes)
Welcome!
About your question, submitting an exist game but on different platform/version seems redundant.
For example, this game has different leaderboards for each version: https://www.speedrun.com/jak2 There are also games versions with different lists, like here: https://www.speedrun.com/ori_series
You should ask in the forums of the game itself, the mods there should know more about the game to help you. There may be no difference at all regarding runs between HD and original version (beside from the visual differences), or a new variable of the game version can be added as well, or something else.
theres big differences in the balancing of the Game between the versions. A few battles made easier, a few harder, powers/spells changed I'd argue the Original is more difficult or unfair even if the 2 are close