I like to leave as many roots as possible and cut them off in a few months after the orchid has secured itself to the mount. Less stress for the plant and more roots to support it until new roots grow.
I agree. Leave as many roots as possible so it has less stress and can absorb more of what it needs. Over time, it will attach and you can clean up. Just avoid cutting what you have to or need to now until its more established on the mount.
I was going to answer the same thing: I would not cut anything off now. All of them look very healthy and will be needed for nutrition to the plant. Mount it securely, let the roots attached and in a few months cut off the ones that look the weakest.
If you are mounting it I would cut the couple that are pointing straight down from the plant and leave any pointing to the sides. You need to get the base of the plant as close as possible to the mount and that won't be easy with chunky roots on its base.
I never cut anything off. Attach it as well as you can. Oftentimes, orchid roots will hang down from a mount and continue to grow, eventually growing together. It's very healthy. And roots that aren't pulling their weight and collecting water will dry themselves out.
Additionally, I mount my phal's downwards. It's natural, prevents crown rot, and prevents spike breakage.