Yeah threatfire wont get along with avast’s behaviour shield so it’s not recommended, best to install malwarebytes for secondary scanning, update it first then run a weekly scan just to check thing’s are ok.
There is a paid version with realtime scanning if you wish to buy but not really necessary.
ThreatFire enter in a very slow development route.
Problem with some applications (like Firefox addons) made me give up on it.
Besides, avast has a behavior shield now and it’s being improved version after version.
The need for Threatfire is a thing of the past. PC Tools actually stopped releasing new versions over a year ago. They now have a newer version but still has issues. Most modern day antiviruses have either a built in BB or HIPS. So the need for Threatfire is history. Maybe people running Avira or NOD32 will gain from it but products like Avast,AVG,Norton and Kaspersky all have a BB built in. CAV uses D+.