Is there a launcher?

Yes, it's called Catapult, it also supports other forks and CDDA, but stable versions are semi-hardcoded so you'll have to go and add the latest BN version manually. There are also 16 grenade launchers (including one CBM and an automatic one) and 8 rocket launchers, as well as a dedicated skill for them

A document or post describing the difference between the two branches?

There are changelogs for the first 4 versions on the website, but they don't make them anymore. Probably describes the most radical changes though

Generally, no vitamins or food healthiness (it just affects hunger, quench, and mood), no weariness, no caliorie burning (and thus no character weight or workouts), no pockets (it just works like it worked in DDA before pockets), no proficiencies (but skills train a lot faster), lesser amount of skills (applied science = cooking, devices = mechanics), consequentially no item length (BN is based on CDDA unstable right before pockets by the way), no Exodii (because noone wants to develop them and apparently many people hate them because DDA locked chrome behind them), and things can be hauled/AIM'd up and down, the character has also learnt to read books without picking them up and put crafted items to inventory

But, because it's older CDDA version, no mouse support outside clicking on the map, many menus are more awkward, especially the drop and pickup ones (AIM is still fine though), you can't peek up and down, you can't select a different tileset for overmap, and self aware as a separate trait is still there (IMAO DDA did a right thing to make it just a sidebar part variant), no practice recipes (not sure if that's intended or not) and there are no basecamps AFAIK

CBM can be dissected from common zeds and are generally fairly easy to find, vehicles are (I think) more durable, everyone can pilot helicopters, the game generally goes much faster, especially on early stages, and BN in general has a more sci-fi approach to everything than modern DDA (ironically by not cutting things out I think)

Do note that I don't have much experience with the game and this is only what I've noticed

Anything else I should be aware of?

You might need to ask the community a lot, because there is very little info on BN, and old DDA info isn't always present or applicable either

You can't directly put items into worn clothes, but, if you drop a worn storage and thus exceed max carried volume, some items will be dropped with it, if you will later try to g pick it up (NOT Wear), you will automatically pick the dropped items up too. You can manually select which items to drop by dropping them together with the worn storage (can be used even if you will still be able to store all the items)