Lucien, the 720nm filter will allow deep red light in. If you photograph an American flag, it would be faded red and white stripes with a gray star union. And I have done that photo. Red tail lights show perfectly red. Skies have a bit of red mixed in the color and become sort of bronze.
Having a pro do a permanent conversion runs $250 to $275. This removes the visible light pass filter in front of the camera sensor and they install new filter with your specification of cutoff wavelength. I personally like the traditional 720nm. The lower number 850nm will give only infrared and the photos will appear all b/w. The other options are shorter wavelength (more visible color). Not as much of a fan of those, but people do make interesting photos. After I bought a 2nd D80 body years ago, I had my old 2001 vintage Coolpix 995 professionally converted. I still have that camera and it works. But it is just 3.4 megapixel and jpg or tiff only. For 2020 I sent off my remaining D80 body (it was the 3rd DSLR in the house) for a conversion and used it a lot last year. Right until it failed. I have not been able to revive it and I won't spend more money on this 2007 vintage body anymore. I'm shopping around for a used body pre-converted since then. The conversion is really the nice way to go since you can handhold and take photos normally. Autofocus and autoexposure are not an issue this way.
At 720nm many people prefer to use Photoshop to swap the red and blue channels with each other so you get a cool bluish sky. I did that a bit in the beginning but I like to leave the channels alone now. If anything I will fully desaturate to a pure B/W if I see this as the way to go for an image.
Here are 2 examples using that Coolpix 995 at the park in Madisonville, KY where I traveled to for the 2017 solar eclipse. I was too busy to try to get an eclipse shot with it though.
And an extended sampling from my D80 conversion last year. Still hurts a bit that it died.
Fully desaturated to B/W to start.
Color left as is next.
With the D80 I basically left the white balance on auto or measured a custom white balance off of green grass. I tended to shoot in aperture priority mode or in P mode. I mostly kept a very cheap 18-55mm DX (no-VR) lens on it.