To add to that I think there can be a 4th category, “ecchi for the sake of comedic relief”. This category can also mix in with the first 3 categories especially if it is a sex comedy type manga but can also be it’s own category. Basically they don’t use ecchi for the sex appeal but for laughs. A great example of this category would definitely be agrivity boys. It has a great amount of raunchy jokes and partial nudity in it but it’s not used for sex appeal but rather to make people laugh. Plenty of manga use this category like dragon ball (during the early parts goku would constantly lose his close as a running gag during/ after battles, JJBA (it uses bizarre sex jokes like the infamous humping scene as a way to get laughs) jungle tar Chan (the main character would constantly get an erection after seeing a girl he finds hot).
There are very few jump series that I think straight up uses ecchi as sex appeal as the main driving force of the manga. Even Harenchi gauken was more of a raunchy comedy manga than a straight up ecchi manga. The only ones I can think of that fits that description are to love ru, yuuna, and of course ayakashi triangle. That is to say that jump ecchi series are surprisingly tame compared to other manga magazines (especially magazine and champion).
