Groups are used to restrict which mods in interact with a given Bodyslide Preset.
yes you can, but the real question is, should you?
deeper delve: (bear with me here...)
Suppose, for instance, that you have CBBE, CBBE-3BA, and BHUNP all installed. (just do, I don't care if you have multiple body types installed or not, this is a story to get a general point across ok?)
Each will be represented by a series of unique Bodyslide presets suited to use for that body type.
Now, to support these, you've installed a bunch of mods, some CBBE, some CBBE-3BA , some BHUNP.
Okay...So now you create "a bodyslide" (ie a Bodyslide PRESET) for your player, in your case, CBBE-3BA
When you finish tweaking the sliders and are super pleased with the results, you, being a very smart person, Save_As that slider set as "MyHawtChik nude body" or "MyBuffDude McDude" (or something to that effect) so you can refer back to it later when you spy some armor named, conveniently enough, "Rilly hawt armor made like SOooo for MyHawtChik body types like man" or "The kind of armor any true McDude would look like so awesome in!" and immediately install it (duh, who wouldn't?) ... Well, now you can fit it to that specially tailored preset you smartly saved earlier for your player or follower or NPC with Bodyslide capabilities)
Ok, as a "tedious, annoying" part of that save operation, you're asked to check boxes for which "wearable" mods will be included in the group used for selection on the body/outfit dropdown... (yes, I find it tedious and annoying but it IS necessary...it's not a flaw)
Generally speaking, while there are always exceptions here and there for any sweeping statement... you wouldn't want to accidentally fit and equip a piece of armor made for BHUNP for your CBBE-3BA player. it would almost surely look wrong.
Get where I'm going?
Groups are used to restrict which clothing, armor, and even body (physics model) mods are made available to interact with a given Bodyslide Preset.
Proper use of the group filter avoids accidentally applying the wrong body type asset to a body or from using a wearable that isn't
for your body type isn't meant for the character you're working on, since not adding a given mod to that preset's groups list, prevents its included items from being offered in the Body/Outfit dropdown when that preset is selected.
Or, it can just be used to reduce the amount you have to scroll in the body/outfit dropdown. If there's some set of items you use for follower bob, or follower sarah, that you never use on player, why should you scroll through all of bob's and sarah's junk in order to find that special bauble you want to adjust or fit to your player body?
Or, for that matter, it can be used to create specific selection of armor, clothing, jewelry, etc offerings will be made for a follower or NPC who has their own special Preset (ex: to avoid accidentally overwriting some player item were they both to allow use of a given mod's assets for Bodyslide fit/build)
Personally speaking, I rarely use batch build, although I have for wigs and a couple other headgear items. I prefer to selectively build so that I can fit, build and assign various items to other people than me, using either bodyslides (ie bodyslide presets) they came with, or ones I've created (ex: followers with disparate shapes and sizes from my own player). I don't wear the red, blue, black , white and yellow shirt. So I can fit the yellow one to Sarah, and the blue one for Greta, and the green one to Iris, and I can fit the black one for me... I mean, how many cool tailored a bit of this a bit of that outfits can you wear? But whatever. I understand the practicality for some to do so. just sayin.
All I can do is try to explain why/how of the groups filtering. So in answer, yes you *can* batch build everything. should you? idk... that's up to you.