HI Mika
You are most welcome, my friend. Glad to be of service.
First and foremost, the site (Hao Family Taiji Meihwa Tanglang in Hong Kong) that you got the Korean PM guys from is a great site that has IMHO the most comprehensive northern Mantis history and lineages as we know it. Unfortunately at this point it is only available in Chinese. Shifu Ilya Profatilov did a great article on Taiji Tanglang (Jiang Hualong-Song Zide lineage) History in English. He used to have some sites that have the information available as well.
Basically for northern PM system, you would be looking at 4 major branches - Taiji, Meihwa, Qixing, and Liuhe. There was confusion about Taiji and Meihwa. At one time, they were grouped together. Regardless of the differences between aiji and Meihwa, they both came from GM Liang Xuexiang (1810 - ? CE). In fact in the old days Tanglang is Tanglang. There was no designation whatsoever.
Personally, I believe the designations serve the purpose from a research angle of where did the lineage came from and how it has developed or matured. For example, Meihwa would suggest to me that the lineage at one point would have something to do with Jiang Hualong. So it is possible to find material or training methodology that is reminiscent of Jiang’s teaching.
From these 4 main branches came the different styles (ie Hao family Taiji Meihwa Tanglang) and hybird styles.
There is a debate going on whether there is such a thing as Shaolin Tanglang which claims to be the oldest and the most direct teaching of the legendary Wang Lang, progenerator of All NPM. Having said that I believe Wang Lang’s capacity was more of an honorary progenerator so that no one laying claim to being the SOLE inheritor of the system. Needless to say, this is pretty much not working as many styles of PM claim to have the one and only real deal. Personally, I find that’s kind of non sense. But then it just me.
As you are a non PM person, you recognize the attributes of PM fighters (those on the clip). This goes to show that PM system and/or its styles is not something that’s on the paper. It is alive in its actions. I applaud your effort in doing the research before committing to the system or style. But at the same time, a leap of faith would shorten the endless search. My advice to peopel is don’t come and observe class; come and practice. Nothing beats the hands on experience in Kung Fu.
I would like to take this oppotunity to comment on the list that you provided, hope you don’t mind. 
<<<<1) Plum Blossom (Grand Ultimate) Praying Mantis>>>
“Meihwa”
This is of mostly Jiang Hualong, who was a student of GM Liang. There are Plum Blossom Throwing Hand which I believe derived from this lineage.
<<<2) Six Harmonies Praying Mantis >>>
“Liuhe”
I have limited understanding of this branch. So I reserve my comments on this.
- Seven Star Praying Mantis
“Qixing”
I think Shifu Tunks, Sifu Cottrell, etc.. will be able to give you a better idea on this one.
In Europe, Lee Kam Wing is quite active. He is of HK branch GM Luo Guangyu - Chu Chi Men lineage. German Bailung here can give you a good idea of how things are like with GM LKW.
Personally, HK seven star could be a seperate style of PM on its own. Also I would go further as to say there could be a Jingwu Tanglang style based on GM LGY’s teaching.
- Eight Steps Praying Mantis
“Babu”
Quite popular in Taiwan and USA. It’s related to Meihwa’s Jiang Hualong.
- Grand Ultimate (HK branch) Praying Mantis
“Taiji” (TJPM)
The HK branch of this is known as CCK TCPM which was taught by GM Chiu Chuk Kai.
Jiang Hualong-Song Zide’s lienages from Shandong also is known as TJPM
- Secret Gates Praying Mantis
“Mimen”
It is a term coined to the teaching Of Zhang Dekuei (sp?) who has TJPM roots. This is based in Taiwan. Tainan Mantis can help you with this definitely.
- Ren Clan Seven Star Praying Mantis
I am not sure of this one.
- Wah Lum Praying Mantis
This is one of the very interesting “development”. I am of the opinion that this has something to do with Meihwa Shuai Shou Tanglang. But there are others here, who actually study the style, can help you with this.
Actually, I thing we could not miss out Taiwan’s Shrfu Shr Zhengzhong. I believe it is semi offical that his branch is named Ponglai Wuji Tanglang. BTW, Ponglai stands for Taiwan.
those that followed are southern mantis. They are not the same system of Mantis as far as I know. There might be some remote possibilities that these are related to NPM as we know it. But that’s an extreme long shot of my own speculations.
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Bamboo Forest Southern Praying Mantis
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Zhou Clan Southern Praying Mantis
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Zhu Clan Southern Praying Mantis
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Iron Ox Southern Praying Mantis
Hope this helps.
Mantis108
PS please feel free to visit my forum (link provided with my signature line below) or email me at sifu1@internorth.com