Antifa tactics are fluid, not static. The discussions of the usage of violence are, unfortunately, quite one-dimensional and do not take into account the history of antifa action and its flexibility. To become monolithic is to become easily defeated.
Antifa is highly utilitarian. The movement is not predicated on teary-eyed idealism, but instead a clear desire to stop the rise of fascism at its roots, by whatever means possible. Thus they refuse the adoption of one-size-fits-all tactics.
Is violence useful in opposition to fascists? Sometimes. If it refuses them a platform, if it marginalizes them, if it pushes them out of the conversation, yes. But does it matter if antifa takes to the streets and gets into fights with the Proud Boys? Not necessarily.
Right now the Proud Boys are defined by their desire to get violent, their pre-pubescent ideology drives them to prove their machismo at every step. It could be highly useful to let them languish in impotence. It all depends on the stakes and the circumstances.
If fascist rhetoric gains traction again, like during Charlottesville, the calculus could certainly change. Charlottesville was a massive loss for the alt-right, an event which catalyzed opposition to their ideology. Their marches now are desperate attempts to regain relevance.
That is all I will say. I will not advocate a plan of action. Those who organize under the banner of antifa will decide that themselves. They are, by their nature, a spontaneously organized collective. Stop trying to dictate to them how to act. They are the ones in the streets.
