The new run will not change my place on the leaderboard so it seems unnecessary, but I readed that speedrun.com is holding the history of runs, so, should I submit the new run if I have a better one on the board already?

only submit new bests. for example if you have a 1 hour 30 minute time on the boards and then you get a 1 hour 31 minute time dont submit it but if you get 1 hour 29 then you should submit it