Hello all! I have a PCB design that will incorporate the use of daughter boards as parts on the board. These daughter boards have through-hole pads on them where breakaway header pins can be soldered to them. I have two questions related to using such parts, one that is "best design practices" based and one that is "ordering for assembly" focused.

Q1: Do you think it is better to put one set of header pins through the holes in BOTH my daughter boards and my designed PCB and solder them directly from there? Or do you think that I should solder female header receptacles to my main PCB, male pins to my daughter boards, and attach them together that way? Assume they will expereince 0 vibration in their use-case. I would ideally prefer the daughter boards lay flat on the surface of my PCB, but I'm not sure if it is good practice to solder a single set of header pins through two stacked through-hole pads. Any advice is appreciated.

Q2: When laying out my PCB in EasyEDA, I was able to find some community-made components in the community library that have the correct pad and stencil layout of the daughter boards I'm using. There are also components in the community library that are essentially individual header pins OR stacks of header pins, with a PCB Component layout looking like a single through-hole pad. I know that in EasyEDA, you can overlay pads of the same geometry over-top one another without getting a DRC issue. I have confirmed this... However, can I just put a set of breakaway header pins on my BOM and inform JLCPCB (or another manufacturer) in the ReadMe that they should solder header pins into those holes and then put on the daughter boards? Or should I model the header pin components directly into the EasyEDA model to simplify ordering?

IF I DO have to model in the pins (assume they are all the same size pin), can I just put a big batch of breakaway headers on my BOM and say "order this"? OR do I need to put each singular header pin on my BOM (ex. putting quantity 10x of a 1-position header pin vs. putting quantity 1x of a 10-position breakaway set of header pins)?

Has anyone had to deal with this before who could offer any advice?

I sincerely appreciate responses! Your input on this is appreciated!