I've always read a lot of paperback reprints of strips (humor ones though, not adventure), 99.999% of them were printed in standard paperback format, usually with the panels rearranged to fit the vertical shape of the book (sunday ones were likewise rearranged). The only ones I've seen in the horizontal format are garfield ones. I always felt that the vertical ones were easier to handle the book, but tended to feel pretty awkward in regards to the layout.
The town I grew up in didn't publish a sunday edition, but the one from erie (approx 40 miles away & the nearest city of equal or larger size) was sold in all the local stores, so that's what we got every week. Once in a while we'd buy a pittsburgh edition (approx 200 miles away), which were only sold in a few stores in that town (but were more common in neighboring towns). It was interesting comparing what strips the 2 papers had/lacked relative to each other.
I never really read adventure strips at all, for the reasons already mentioned, combined with a lack of interesting looking ones. The only adventure strips I ever read at the time were spiderman (I've been a spidey fan since before I can even remember), and occaisional spurts of dick tracy and phantom. Those were the best of what was in our papers. We didn't have popeye, nor any sci-fi strips, nor anything else which was ever even remotely interesting. In fact, I think the only other comic we had which could be classified as adventure was prince valiant (which I think I did actually read once in a rare while, now that I think about it).
The paper we had contained mostly humor strips (thankfully). Beyond the handful of adventure was I already mentioned, there were a couple soap opera strips such as dr morgan (or something like that) and some other one with a woman's name in the title, mark trail (sort of an educational strip, I guess), and a couple hard to categorize ones like doonesbury.
You're right about most adventure strips having semi-independant runs weekdays vs sundays, and usually a summary on the sunday strip. While that setup is far better than being forced to read every single strip each week, it still left the problem of limited content per week (in fact, having to use the space for the summary each week reduced the available space even further). Two full weeks of strips contain less story than is found between a single pair of commercial breaks on any TV show.
Back in the 80s, our sunday paper had a big comics section, with 2 full, double-sided broadsheet pages of comics, with each strip having the full width of the page. Later they started reducing it to 7 of the 8 "pages", reducing the size of the strips, and sticking in some in vertical arrangements (the back of the comics section would be a full page ad, usually for a local car lot). Later they ditched that backpage ad, but reduced the middle sheet from a broadsheet to a tabloid size, leaving only 6 "pages" of comics. Then in the mid 90s or so, they reduced it to 5 "pages" plus 2 strips, and used the remaining 2/3~3/4 of the back page for more educational content (primarily a "fairytale from around the world" text segment, plus some kind of facts/trivia thing). Each time they reduced the physical space available to the comics, they both reduced the size of each strip & reduced the number of strips. The last time I looked, they had shifted the whole paper to a smaller format (still essentially broadsheet, but about 20~30% smaller in each direction. I don't know if it's the "berliner" format or just some arbitrary/custom one), reduced the comics section to a single "berliner" sheet (4 "pages"), with half of the back page being the aforementioned fairytale thing, and strips being squashed & crunched to fit about 6~8 to a page (in addition to vertical arrangements, many are squashed into a square arrangement, placing 2.5 strips (2 squares, plus about half of a veritcal strip) into the space formerly filled by just 1.