I am not sure how big they are compared to k. multi but it also depends on the type of jacksons, there are 3 types, J. merumontanus (Mt.Meru dwarf jacksons, tiny guys), J. jacksonii (small jacksons not as small as merumontanus and are found in Kenya) J. xantholophus are the bigges jacksons and are most commonly sold, I dont know how hard it would be like to find them in Canada.
The bigger the cage is always better, 60cm X 35cm X 35cm should be minimum for jacksons, and only one per cage.
I cant comment on Quadricornis as I have never seen/cared for them in my life.