Do you think that posting there occasionally will:
a. Count as backlinks
yes, but usually a bad one, or one that will be bad soon (because everyone and their dog will happily get free "quality" guest posts to the point where the entire guest posting site will be filled with all sorts of irrelevant / shady / idiotic articles on CBD, gambling, viagra, dog grooming, wedding dresses, local plumbing, how to put makeup on, gay services, etc... Will you want a backlink from such a website?)
probably, but...
The sites don't look great, but they tend to have +30 DA.
the last time google cared about DA when ranking sites was - according to my knowledge - NEVER! Just screw the DA, DR, and all other 3rd party metrics that companies like Ahrefs, MOZ etc have invented. Google only care about their internal metrics, and their internal metrics are usually unknown. DA and DR are just guidelines, but even then, they are the last resort type of guidelines...
What matters when assessing the quality of a website is how google sees that website. Is the site ranking and getting google traffic? Does it have 1000s or millions of indexed pages and keywords that it ranks for? Do 100s or 1000s of those 1000s / millions indexed pages get even 1 visitor per week CONSTANTLY? Then google likes that website and any link coming from any of those indexed and traffic'd pages is worth gold, and these are all of the metrics you need to concern yourself with.
The only thing you should pay attention to when checking the sites' stand with google is looking at the trends for the last 6-12 months. Did the number of indexed pages, the amount of traffic, and the amount of ranked keywords increase (or at least stayed constant) over the last 6-12 months? Then it's a good site. Did these numbers drop constantly and seem to tank into oblivion soon? That's a clear sign that google have flagged / marked that website for whatever reason that their retarded brain has invented and they'll soon get rid of it . In this case you might not want a backlink from that site.
But otherwise, if the stats are growing (or at least constant) it's a good site...