Reports are handled by the Instant Feedback System (automated). After you receive too high a density of reports, as in reported in too high a percentage of your matches, it will check your logs and gameplay for the offending behavior. If it finds the reports were false they won't hurt you and those that made false ones will lose weight in their future reports.
It's probably important to note here that threatening to report people and making accusations is a toxic and punishable offense in itself, so while their reports will have no effect on you if you didn't do those things, your reports against them for harassment will have weight.
https://support.riotgames.com/hc/en-us/articles/207489286-Instant-Feedback-System-FAQ-