It's not a comprehensive list, but here's what I now of as I have picked up most of these since they launched as well... the caveat, this is all off the top of my head, so there could be errors...
The first wave of books were the Walmart Exclusives and there were only 4 titles...
Teen Titans (ran 7 issues)
Superman (ran 16 issues)
Batman (ran 14 issues)
Justice League (ran 7 issues)
There was also a Holiday Special and a Swamp Thing Halloween Special as part of the first wave.
The second wave replaced 2 titles and added a few more and were still Walmart Exclusives. So it expanded from 4 to 6 ongoings.
Titans (replaced Teen Titans) ran 7 issues
Wonder Woman ( partially replaced Justice League) ran 7 issues
Swamp Thing (ran 7 issues)
Flash (partially replaced Justice League) ran 7 issues
There was supposedly a Detective Comics anniversary special that was part of the second wave, I never saw it.
All books (except Specials) were released monthly, all featured 12 page lead stories that were new/original and 3 reprints from different eras (all post-2000 stories though)
All the titles ended when the Walmart Exclusive period ended. There was a new phase of the books launched where the books were available both at Walmart and through Diamond.
The Walmart versions were released about 3-4 weeks before the direct market versions, but had reprint/recycled art covers. The direct market versions had new cover art commissioned specifically for the books.
I am much less certain what has come out for these (I've gotten most of them through the direct market rather than Walmart and distribution was disrupted by Diamond's shut down, so I've seen a few things at Walmart I hadn't seen in the direct market but it may have been solicited just not released yet. Distribution frequency is more variable and sporadic. For regular ongoings, books are released 6-8 weeks apart. Limited run books might be monthly or every 6 weeks, and there were a lot more one-shot. Content vary as well. Most of the regular/ongoings have 2 new stories of 10-12 pages in length, one by a regular creative team and is somewhat continued, the second can vary creative teams and are complete standalones for the most part, but might reference something in the lead story. There are usually 2-3 reprint stories form various era included (again all post-2000 for the most part). The limited run and one-shots vary the type of content they carry.
The ongoings that I know of have had 3 issues released and the 4th of most are coming out currently, some have appeared in Walmarts but haven't hit comic shops yet, and include...
Batman
Flash
Wonder Woman
Swamp Thng
Aquaman
Superman is also an onging but started later than the others due to delays in Tom King finishing his 12 parter that lead to the first wave Superman book to include a pair of fill in issues and run 16 issues rather than 14.
There's a Titans book that looks to be an ongoing that started even later, but it has only had 1 issue so far.
Where it gets wonky is the limited runs and one-shots. DC is using a lot of titles form their catalog to show use to protect trademarks it seems by doing one shots with them.
What I know of...
-There have been a couple issues each of Super-Hero Girls/Super-Hero High and Tiny Titans-I haven't picked these up so not sure how many of each.
-There was a Scooby Doo book and a Ghosts book that were part of the first wave of these releases, but both turned out to be one-shots not ongoings, but were not announced as such.
-There were 2 Crisis on Infinite Earth issues that featured Arrowverse (CW) characters in the new/original story content but had reprints of the classic Wolfman/Perez series
-There's a science fiction oriented one-shot using the From Beyond the Unknown (I believe, I am not sure on that title-I ordered it when solicited haven't gotten it yet)
-There was a World's Finest book featuring Batwoman and Supergirl-I think there is more than 1 issue, not sure if it is an ongoing yet or not
-There's an Our Fighting Forces issue-has a Kubert cover form Walmart, direct not released yet. It features a new story with Jim Lee and has been getting snapped up by speculators, so has been hard to find. I did grab a Walmart copy of this one to get the Kubert cover but I only saw 2 copies and one was badly damaged.
It's not completely comprehensive, but that is the bulk of the releases so far. I'll dig around the pile of these books I have to see if I missed anything. There may be one or two more one-shot type books I haven't seen yet out at Walmart that haven't hit the direct market yet so I haven't seen them. Hope it helps.
-M