How to make "melee wave" or "sword wave"?

I dont even know what to call this. I will just show some pictures:

What is the optimal way to do it with good performance?

You need a particle emitter, and a skeletal mesh with two sockets. Then use the Set Trail Source data node to assign the trail to the sockets. The trail variable is a particle emitter component, added to a weapon blueprint, with an assigned weapon trail effect/emitter.

Or you can use the play emitter notify directly inside an animation, but this needs more manual fine tuning for each animation.

The free Infinity Effects package from the marketplace contains weapon trails.

Seems like a animtrail particle emitter would be best. Here is a basic tutorial on them Linked below.

And a second one with an actual sword example.