MalwareBytes & Hitman Pro are the softwares which are run when ever you want to scan a particular file or folder, & whereas Avast is Anti-Malware software which always protect you from viruses as it run in the Ram all the time.
MalwareBytes(Free) & Hitman Pro do not always run in the RAM.
MalwareBytes(Free) & Hitman Pro do not provide Real Time Protection so they do not conflict.