When I did my research, I was trying to understand if Apple’s charge for their SSD upgrades was at all reasonable, and considering the cost of the X5 I decided it was…but the specs are overkill for a lot of use cases. That X5 and others of its ilk are pretty sensational demonstrations of the power of Thunderbolt 3.
Just testing my MBP from 2017 with an 18.2GB file, I found the T5 4x faster than the external HDD. These were copying the file to the external storage.
Seagate 4TB HDD: 280s
Samsung 512GB T5: 70s
This relates reasonably well to data that puts the Seagate at around 115 MB/s and the T5 at 550 MB/s. That data suggests an internal SSD or Thunderbolt 3 external SSD will be between 1500 and 2500 MB/s depending on size and brand (numbers from my memory).
So, you will certainly see improvements with the more expensive option, it’s just up to you how important that time is. If it is work, the cost is likely to be worthwhile. For my hobby, I’d rather wait a bit and keep only 1 or 2 working projects on the expensive storage. Again, it depends what some video editing really means.
One consideration is future proofing. If you buy a 1 or 2 TB internal SSD then it is most likely only going to last as long as the computer. If you instead invest the same money into a 1 or 2 TB external, Thunderbolt 3 SSD then the drive can move to new computers as you upgrade.