The differences between the Northern and Southern Shaolin Temple styles is a vast and contentious subject of debate both within and outside of China! One school of thought suggests that the Qin Dynasty (221-206 BCE) - although relatively short-lived - set the blueprint for everything we now associate with 'Qin-na' (or 'Sina' as the Romans referred to it)! It is said that every village was turned into a military barracks and that the Qin government issued an 'official' martial arts manual (premised upon 'Longfist') that was to be replicated throughout the empire! Although not yet discovered, if such a manual existed it would have been a cross-reference of all the known martial arts styles of the day. The best and most effective movements were chosen which are still practiced today.
The thinking is that this single 'synthetic' style provided everyone with a single style which then 'evolved' into the hundreds of styles we know today after the Qin Dynasty collapsed and there was no longer any official pressure to keep the style exactly the same in all places! (The Qin introduced the idea that the same 'law' should be applied in all places and at all times for all people - Confucius had disagreed with this 'legalist' concept - stating that the upper-classes should do as they please whilst the peasants must be kept in order with severity). A modern equivalent of this type of manual is that of General Qi Ji Guang [1594～1644] (戚繼光). In fact, Chinese records state that he was a very well respected armed and unarmed martial artist who had trained with many renowned martial arts Masters and had applied these techniques on the battlefield! He wrote around forty volumes of books regarding martial and military matters. One that you might find interesting is his '拳经捷要篇' (Quan Jing Jie Yao Pian) or 'Fist Classic Victory Assured Record'.
It is said that General Qi Ji Guang took 32 of the best unarmed movements that he knew and combined them into a single 'Form' (Kata) that could be easily taught to soldiers and Officers! Therefore, this manual is a historical snapshot of many of the martial arts styles that existed during the 16th century CE. This is an interesting Chinese language page entitled 'Qi Jiguang's Experiment: In Order to Adapt to Military Needs - Innovating Traditional Martial Arts!' (戚继光的试验：为适应军事需要，革新传统武术拳种) - which contains a number of pictures from the above-mentioned manual:
This manual serves as 'evidence' - as opposed to 'hearsay' - or perhaps adds weight or takes weight away from legends and stories. As for the Hakka people - when they lived in Northern and Central China they practiced Northern martial styles - but when they migrated Southward - there was far less living room and so many Masters 'shortened' their styles - our Masters (in our family style) refused to do this and so we still have the old 'Northern' versions. Villages to the left and right of use, however, all practice the shortened (Southern) versions of Praying Mantis Fist (螳螂拳 - Tang Lang Quan) or developed shorter and more compact styles such as 'Iron Ox' (铁牛 - Tie Niu). Wing Chun (詠春) is a Cantonese art and so was not practiced in Hakka villages in the old days. Interestingly, in Fujian province, the Hakka people built 'Round House' fortifications so that all their life happened within the safety of a fort enclosure. This lack of space led to shorter martial styles. The Hakka-Punti Clans Wars (1854-1867) was fought between the Hakka and the local (Cantonese) people and killed about one million or more! (See: https://files.geistlib.xyz/sharing/rec/被遗忘的战争%2C咸丰同治年间广东土客大械斗研究%20-%20刘平.pdf). The Hakka were defeated and for a time their culture was suppressed - including their martial arts (which had to be hidden away or altered to look like indigenous martial arts)! Our ‘Chan’ (陳) martial lineage had settled in the Sai Kung area of the New Territories around 1600 CE and escaped from any direct Qing Dynasty pressure during the 19th century. Although Master Chan Tin Sang knew many of the ‘shortened’ Southern styles - (the family village next door was the ‘Lim’ - 林) - as he was the Clan Leader (Chief) the inner circle practiced the older and more prestigious ‘Northern’ styles of ‘Longfist’ (長拳 - Chang Quan) - which is what we preserve in South London. Gee is next in line (and our two daughters).