Hi again Liz. The setting I use, Relative Colorimetric, is not due to the Canon printer, but for color print accuracy.
It has to do with rendering and the Perceptual will change the shades of colors to pull them into the color gamut of the paper and the printer. It does that with the entire image colors' Perceptula pulls all the colors.
Relative Colorimetric says, "Hey, I sent you this red, and that is what I want. If a shade is not printable then it's OK. If it finds a shade slightly out of gamut, it will pull that one back in. NOT ALL colors, just the small shade that is out  of gamut.
I find that my prints match the original profiled image with my camera profile.
Hope this helps.
Fred
PS Maybe Mike can be more on point if he has time.

This may be of help
https://www.cambridgeincolour.com/tutorials/color-space-conversion.htm
Terry

Thank you Fred and Terry! I had actually done some Googling so I had read articles like this, but I find the language a bit arcane. For me the underlying question becomes, how would I know if any colors in my image were out of gamut? I don't know where the gamut starts and ends!

I will probably have to bite the bullet and do some test images.

Also--re: black point compensation. I see Fred ticks that, and I never had. Is that considered the default thing to do? (As you can see, I am looking for the best "defaults"!).

Thanks again.

Liz

OK, so that being said, should I use Relative or Perceptual for printing my photos? Or is it irrelevant?

Let's try an analogy.  We have two painters with initials P (for Perceptual) and RC (for Relative Colorimetric).  Both of these painters (P and RC) have the exact same paints (inks) to work with when they try to paint your photo.  Let's see how they make USE of those paints:

RC: RC is the technical painter.  He likes to be as accurate as possible.  He arranges his paint palette so that if he sees a certain shade of green for the grass in your photo, when he dips his brush into that color in his palette, the color green that is painted is an exact match to the green of the grass in your photo.  When he gets to a bright yellow flower, however, he is able to dip his brush in the correct shades of yellow for part of the flower but the brightest shades of yellow in the flower are brighter than the brightest yellow paint he has (they are out of gamut).  What does he do in those areas?  He might add a little white to his brightest yellow, or add a tinge of green in order to get some detail there.  When he is done, the whole painting has accurate color except for those out of gamut areas: only those out of gamut areas are "faked" with different shades or brightness to try to make them look reasonable.

P: P is the artistic painter.  She doesn't care about accuracy because she wants the whole painting to look smooth and "fit" within the colors of her paint palette.  So she waters down all of the duller colors in her palette, leaving the bright colors alone.  Then when she paints, there is a wider separation between the less saturated colors and the more saturated ones.  None of the colors in her final painting are accurate, but if she runs into a bright yellow flower like RC did above, she can paint a yellow that looks brighter than it is due to the rest of the painting being "watered down": she still can't paint the correct/accurate yellow but it'll look like a brighter yellow than RC painted above.  And the "watered down" painting still looks OK because the eyes adjust for the lower contrast.  Further, if that bright yellow flower is the focus of the painting, her version may look better than RC's above!

Final word: I like RC.  Why?  Because I know that RC will put down accurate color for every color that my inkset can render: it's only "off" for the colors that are out of gamut.  And even more important, a lot of my photos may not have any out of gamut colors in my main subject: in these cases, the whole picture is accurate WRT color.  With P, none of your colors will be accurate and more importantly, even if your photo contains no out of gamut colors, they still won't be accurate with P: they'll be watered down.  That's because P waters everything down by the same amount, regardless of what your photo looks like, just "in case" you run into very bright colors that are out of gamut.  So in a sense, P is overkill for most photos and may make them look dull.  BUT, it's there in rare cases where you may have a very bright yellow flower or maybe a shiny red fire engine that you want to "pop" with respect to the rest of the photo.

Best I can do...
Mike

Don't forget the out-of-gamut check, which I find quite useful. Use your soft proof button at the bottom, then check the gmt box to highlight the out-of-gamut areas.

I did not know anything about this! Must pursue...