Great analysis.Very similar to a OWC Thunderbolt 3 Dock, except they replaced FireWire with USB 3.1 Gen 2. The OWC audio port combines headphone and microphone ports. The OWC is just missing a USB port which is strange since internally it appears to have an unused USB port in one of the two FL1100 USB host controllers.
The CalDigit has 83W of charging for the computer (same as MacBook Pro charger). The OWC only has 60W of charging.
Thunderbolt 3 docks only have four PCIe 3.0 lanes to use from the Thunderbolt 3 controller. Typically, the lanes are used for:
1) USB 3.0 controller (4 ports)
2) USB 3.0 controller (4 ports)
3) Ethernet controller
4) FireWire or USB 3.1 gen 2 controller or whatever
Audio and SD Card Reader each use a USB port. A single USB audio controller can support optical and analog input/output. The capabilities of these devices will differ between docks. For example, the CalDigit uses a faster SD Card Reader (SD 4.0 UHS-II) than the OWC (SD 3.0).
The Thunderbolt 3 controller also provides two Thunderbolt 3 ports (can be used for USB 3.1 gen 2 and display) and a DisplayPort 1.2 or HDMI 1.4 port. DisplayPort is preferable because it's easier to convert DisplayPort to HDMI (DP++ includes HDMI 1.4 so passive HDMI adapter can be used - active DisplayPort 1.2 to HDMI 2.0 adapters are not expensive compared to HDMI 2.0 to DisplayPort 1.2 adapters).
A dock could add more PCIe lanes by including a PCIe switch but that would greatly increase the price (see for example any Thunderbolt 3 PCIe expansion box with more than 1 slot - Sonnet has many examples of single slot and three slot solutions to compare).
A dock could add more USB ports by adding a hub. Does there exist USB xHCI host controllers with more than 4 ports? What USB 3.1 gen 2 controller does CalDigit use? I wonder why they didn't use a two port controller or if they did, then why didn't they use the second port?
(Edited to include other differences between OWC and CalDigit docks)
The OWC unfortunately has had some terrible reports, and what with the limited power, both contributed to making many users skip buying one. While not perfect, the CalDigit has better specs overall – obviously likely as it's the latest, being released recently.
Many would love a switch type thing so they could plug one (or even two) LG 5K displays into two TB3 Macs, and easily flick between them. As the trouble with these displays is they only have the single TB3 input. (Even if you couldn't use the 3 5Gb USB-C ports on the displays back.)
Kanex used to make one for Apple's DP 27" Cinema Displays that had a single press button, to allow switching between two Macs, but never seen such a thing in the Thunderbolt display era (TB1, 2, or now 3). Hrrmpf!
Your last two paragraphs are interesting, love to hear some further (understandable) explanation/examples on those points.