I have the B+W NDs screw-ons sets in various sizes.
Haven't used the 3.0(s) since back in the 5D2 days, & when I did always stacked a Tiffen Hot Mirror on top, but never loved this solution.
I don't know of a better brand for screw-ons at this strength, but would be interested if you found otherwise.
Different sensors have different responses to IR, & no one brand's filters work equally on all, rather it's the case of choosing the best optimized for your particular camera.
thanks bern. my choices seem to be ;B+W or Heliopan at this point ...... they are going on a BMC camera that I should have next week so the IR effect will need to be tested. Base iso is 800 for best DR, and shooting at F2 will look like F 5.6 so I am getting ready for needing at least 10 stops if shooting in daylight. And I will be shooting pro res, not raw, so will want my WB clean as possible.