As for brands, there are a number of major ones that sell in the US:
ABU (ABUniverse) is a brand that lots of people are fans of. They especially have great designs, quite baby-ish. They have 2-tape diapers that replicate baby diapers, especially their Super Dry Kids which the design is based on an old baby diaper design. They also were the first brand to release positional printed diapers in their Little Kings and Alphagatorz, where a specific pattern can be printed for a single diaper instead of a continuous repeated pattern from which diapers are cut, allowing for designs to be right side up on both sides of the diaper, just like baby diapers.
Tykables is known for having hook and loop tapes for all their diapers, which allows for more easy adjustments, better tape reusability. They used to be all plastic-backed, so a unique combination of plastic backing with hook and loop tapes, but they have now come out with some cloth-backed diapers, which are unique in their own right because they use a full thickness plastic layer underneath the cloth-like cover, so you still get the leak and odor protection of plastic-backed while the outside feels like cloth. The recently switched almost all their designs to be positional printed, which some people like and others don't like the redesigns; it's up to personal preference. They also do have a camo design that people like for being not baby-ish, and I like because it feels like a diaper version of camo Goodnites. Their diapers also have a "waddle cut", where the middle is wider to promote waddling.
Rearz is based in Canada, but will ship to the US and also has US sellers (and can often be found on Amazon, although more expensive). They have a variety of designs and features that is neatly summarized in
this guide. They have some very high capacity diapers, but beware their capacity calculation system isn't exactly the same as other brands, so it's mostly useful to compare among their own diapers rather than across brands. Some of their diapers also have moisture-activated scents, which I believe is unique to them.
Bambinos is the OG of ABDL diapers. They were one of the first brands to make and sell diapers designed for ABDLs, with higher (at the time) capacities and cute designs. They have since stalled in their innovation, but still have something unique in their Magnificos which have stretchy wings like baby diapers. They often run sales, so sign up for their email list to hear about them; don't pay full price for their diapers. Their capacities are lower than the other modern ABDL brands, but that can be enough for some people.
LittleForBig seems to be a brand more geared towards DDLG, so their products are targeted more towards women I think. But their diapers can be pretty unisex (and colors/designs don't necessarily have genders anyways). Some are not a fan of the brand because of their transphobia (from what I've heard). Their diapers are generally middling in capacity, more towards the Bambino end than ABU/Tykables/Rearz. They have also hopped on the positional and cloth-backed trend.
PretendAgain is one of the newcomers to the field, but they have put out a great product of TryAgains (their only diaper design). It is a cloth-backed diaper similar in build as Tykables, with the thick plastic layer under the cloth (I personally think they're made by Tykables lol). People have raved about the design and performance; the performance is the same as Tykables but with a cuter design in some peoples opinions.
Kiddo diapers are also available in the US now. They have the Teddy Ultra which is a cloth-backed 2-tape diaper, one of the only ones I believe. They also have Kiddo pink and blue which are based on old baby diapers, with 2-tapes, in the same spirit as ABU's SDKs.
NRU (NappiesRUs) is a UK-based company that sells some of their prints in the US via Tykables' website. They are the makers of Str8Ups, which are solid-color diapers that have a reported 8000mL capacity.
LNGU has a number of positional printed designs that lots of people like, especially the Big Ears Babys. They are cloth-backed positional printed and very baby-ish. Light/pastel colors.
There might be a few other brands available in the US, but these are pretty much the major players currently.