A/. "بِضْع = a few or several " : a word denotes an unspecified number. However, at least three and no more than nine. Therefore it is treated like these numbers (from 3 to 9), masculinize (بِضْعَ) with the feminine counted items, and feminize (َبِضْعَة) with the masculine counted items (It disagrees with the counted item). So as mentioned "بِضْعَة" is the feminine form of (بِضْع). Examples : 1. بِضْعَةُ رِجالٍ = A few men. (In Arabic it means from 3 to 9 men). Here "بضع" came suffixed with ـة as feminine form (بِضْعَةُ) because the counted item (رجال = men) is masculine. 2. بِضْعُ نِساءٍ = A few women. Here "بِضْع" came as masculine form (بِضْع) because the counted item (نِساء = women) is feminine. 3. ومنذ بِضْعَةِ أسابيعٍ اختنق بعض الشباب حتى الموت = A few weeks ago , some youngsters suffocated to death Here "بضع" came suffixed with ـة as feminine form (بِضْعَةُ) because the counted item (أسابيعٍ = weeks) is masculine. PS : I used as well "بعض = some" in the 3rd example. It (I mean بِضْعَة/بِضْع) can be added to tens but not to hundreds or thousands. Maybe it's the case when you don't remember the exact number or you have doughts about it. Examples : 1. بِضْعَةٌ وَعِشْرونَ رَجُلاً = Twenty men and a few. (I don't know if it's true to say that in English). 2. كَلَّمْتُ بِضْعَ عَشَرَةَ امْرَأَة = I spoke to ten women and a few. B/. "بَعْض" some - an unspecified amount or number of. Examples : 1. في بعض الحالات = In some cases... 2. أعطيت الرجل بعض النقود ليحضر بعض الطعام الجيد = I gave the guy some money to bring in some decent food.

My answer is for the second part of your question, I don't use them in my daily life so I wasn't know the answer before googling. As I understood: بضع refers to quantity between 3-9 so you should apply same feminine masculine numbers rules when you use it. If you don't know feminine masculine numbers rules let me know. I've found some examples, جاء بِضعُ نساء وبضعةُ رجال وبضع عشرة امرأةً وبضعة عشر رجلاً شَاهَدْتُ بِضْعَةَ عَشَرَ رَجُلاً كَلَّمْتُ بِضْعَ عَشَرَةَ امْرَأَةً بِضْعَةٌ وَعِشْرونَ رَجُلاً بِضْعٌ وَعِشْرونَ امْرَأَةً مَكَثَ بِضْعَةَ أَيَّامٍ بِالجَبَلِ زَارَنا مُنْذُ بِضْعَةِ أَعْوامٍ

بعض : some بضع: a few

بعض : some بضع : a few

بعض : some بضع: a few