Thanks very much for that valuable feedback. Your explanation on the CPU vs GPU functionality helped tremendously. Per your explanation the with the graphics core having a big roll in video playback perhaps therein lies my problem. I currnetly use Intel's Skull Canyon NUC which is capable to load and run DaVinci Resolve but as previous mentioned is not smooth, the graphics and CPU are as follows:
Intel(R) Iris(R) Pro Graphics 580
[Intel(R) Core i7-6770HQ CPU @ 2.60GHz, 2592 Mhz, 4 Cores, 8 Logical Processors
Although 6th generation on the CPU that in and of itself is still fairly robus. Intel's Iris Pro Graphics 580 I presume is the problem point, not being powerful enough to handle the 4K edit and playback demands. I hope the upcoming Intel Hades Canyon with the discrete AMD Vega graphics alongside Intel's 8th generation processor on the same die should easily rectify this situation. Intel is touting this as being the most compact high frame rate gaming machine and good enough for VR as well. If so, it should handle 4K video editing as well.
On the mobile front, all I have for now is the ASUS F510UA (more on that below) It also will load DaVinci Resolve but with similar results as the Skull Canyon described above. I guess this again is attributable to the integrated Intel graphics which is not much of an improvement over Iris Pro 580.
Intel UHD Graphics 620
Intel Core i5-8250U, CPU 1.60GHz, 1800Mhz, 4cores / 8 logical processors
To conclude, then perhaps I should be able to do my video edits with a new Coffee Lake-H based Core i7 versus the Core i9 unless I have the money to afford the latter. (retired here in Tokyo) I want to avoid eGPUs if possible for both home use and mobile machine. Thus these considerations of Hades Canyon and Coffee Lake-H equipped machines. The Coffee Lake-H equipped mobile laptops will have 6 cores in the CPU and if the laptop is also equipped with the mobile version of GEForce 1050 or 1060, I think I should be OK for video. At least thats the impression I get per that YouTube video link you provided. I will also visit BlackMagic's forums on the subject matter as well. Thanks for the guidance.
ASUS F510UA
Aside from NLE video production with DaVinci Resolve, the machine performs very well for pretty much any other routine tasks, including photos editting. I am quite happy with the machine. I also tend to like ASUS myself as you generally get more bang for the buck on price versus your typical HPs and Dells, which also source their components from Asia anyway. Considering it only costed $499 USD at Amazon U.S. when I purchased it and it incorporates an Intel 8th gen processor, 4GB RAM, 1TB HDD, you really can not go wrong for the price. I would like to have a touch screen, metal case, 2-in-1 convertible as well, but then for this price, beggars can't be choosy. I watched a YouTube video on how one guy having the exact same machine opened the base plate, removed the hard disk and inserted an SSD in it's place. After removing the dozen or so screws, it was a bit of a hassle to remove the base plate, but being careful and meticulously prying the seam open bit by bit with a guitar pick, credit card or some similar slim plastic instrument (not metal) it is doable. To my surprise I also found an M.2 slot in there as well which is not indicated in the description when purchasing the F510UA. I reckon it's there for when the want to up sell higher end models using the same motherboard. Anyway, I did upgrade to a total of 3TB SSD (M.2 x1TB and 2TB x 1 SSD). I removed the 8GB module (single slot) and replaced with 32GB using both slots. (You can see my initial post in which I provided a link to my Google Photos albums describing what I did.) Everything works fine. And in theory should be a nice powerful mobile unit for my video requirements. But alas, the integrated Intel graphics just isn't quite enough to the video task.
Anyway, for your friends needs, aside from the video for routine tasks it is a very decent machine for the price. Heck even Chromebooks can cost that much and more, but here you are getting an 8th gen processor-equipped full-fledged Windows machine. Price went up to $549 I noticed since I purchased from Amazon U.S. Early this year they had a special on it at $499. I also skim over purchasers' feedbacks before making a purchase. 4 of 5 stars is not bad for over 250 reviews. The body is plastic not Macbook-ish type of aluminum, but still has a confident sturdy feeling and lightweight as well. Battery life could be better but still fairly decent. I hope that helps.
Cheers,
Jerry