Printers achieve resolution by moving the paper and making multiple passes. Epsons do the math for you, so with a current Epson printer so you just indicate the final resolution and it will make the appropriate "passes", between 1 and 8.
I had a canon 6100 before going back to epson and it worked a little differently. I'm not sure how the current canon interface works but with the 6100 basically you did the math ... you would select the dpi and then the number of passes, so to achieve a full 2400x1200 resolution, you would pick 600 dpi and 8 passes (I believe the head has 300 nozzles in an inch).
The 63/8300 and 83/8400 series of Canons dramatically improved the dot shape of the printers, resulting in a much more "round" dot and improvement in very fine detail. I"m not sure if they simplified the method to achieve maximum resolution, but I believe now they have something called "print mode" which seems to control the number of passes. What is confusing is they have a "highest" and a "Highest (max. no. of passes)". I'm not sure if that means highest is actually less the the full passes so it's printing at less the 2400 dpi, or if highest is 2400 dpi and the other option enables a setting similar to what Epson calls super microweave which uses 6 passes instead of 4 when in 1440 dpi to get better results. So it may make more passes and change the spacing in order to achieve a higher quality, yet it's technically still 2400 dpi.
Plenty of Canon users here, so perhaps one of them can clarify this. It does sound from the description that for the best photographic results the highest (max. no. of passes) is the best setting. Obviously the more passes the longer it takes to print a print.