The early levels are pretty bad with toxicity. As all the It gets much better after you hit lvl 30.
Also, you don't need to call for reports, as 1 report is the same as multiple reports. It flags the system to check for toxicity against them, if found toxic, they system will ding them and build a case against them. If there isn't any toxicity, then the report will get thrown out.
Which also means that you don't need to worry too much about people threatening you with reports. But make sure you do you job in reporting them.
What sucks though, is the visibility the reporting system provides, as you don't get any punishment notifications if the game you reported someone else was just building a case against them. You'll only get the notification if your game you reported was the game the last straw the person got punished. We also aren't sure if you get notifications if someone was just punished with chat restrictions. Thus it can feel like your reports don't do anything ! But it actually does a pretty good job in getting the needed people punished, so do report them afterwards if you feel harassed.