Ahh yeah good questions my man. I don't mind helping since I can see your brain is working.
The best resource for bing carbs is https://myronsmopeds.com/category/bing-menu/
If you go down below you can see the different numbers (1/14/152, etc) and what guts came in them. The combo there I posted is just something I've found runs well, the 51 slide has the 'buddy hole' which you can add to any slide, it helps out idle better and gives it a little punch out of the hole when you crack the throttle open.
Myron's really explains it better than I can, Ken posts really good stuff about Bing tuning too but it's always incoherent and one size fits all. I have a recipe that works pretty good on mild PP kits and ported stock, is it the best? I dunno but it runs really good on this kit and like 70 kstar type stuff and ported stock. I would be into trying a different setup but this is just what I happened to stumble onto and I've had the same setup on a few bikes and it usually runs pretty good.
You can always go back to the stock posted combo and modify from there but the air filter makes such a big difference that it's tough to use any of the stock settings on a kitted bike with a performance filter. You can also see what atomizers and needles were originally fitted together as a rough guide.