But it surely can attemp cross-site scripting, send phishing and spam messages, broken requests and look for exploits.
Also TOR is generally so slow I don't think there is even the possibility of generating enough traffic for a DOS.
It would depend on the website's resources and services. For example, a layer 7 DoS which just queries an expensive endpoint on the website over and over may not need high traffic volume to overload the website's systems.