For me, it's #4, insert FX only. I'm a computer musician foremost so I have no attachment or interest in the traditional mixing desk or indeed the Console View that emulates it. That means that I do all my work in Track View, with the controls next to the track, and this has only become
more important to me in recent years as plugins have moved from simply being 'effects' to being instruments or simulations that sit squarely in the middle of an FX flow. I need to see those plugins clearly in Track View right alongside the track name, panning, and volume and have quick access to them and their properties, just like I have if I'm using a synth - not hidden away in an FX Chain in a ProChannel that I'll only see if I click on an individual track AND the Inspector is open. (And yes, having to insert FX Chains for each FX in the PC feels fiddly compared to just being able to insert individual VSTs.)
The ProChannel is out of sight, out of mind, and out of my workflow, sadly.
Now, if they were to replace the FX Bin with a minimised ProChannel, and let us mix and match PC modules and FX modules freely and conveniently in that bin... then things would be different.