Since I started using FreeCAD, several years ago, I have been watching the various assembly workbenches evolve. I've been using A2Plus for a while, probably only since 0.18 and since, maybe last July, 0.19.
I saw Assembly4, tried it couple times, but kept using A2Plus because I already knew how to drive it.

I saw this tutorial mentioned on the FreeCAD Facebook group and have now gone through it and the written version. And looked at the second tutorial.
I curious about some things.
From what I've observed there are some requirements with Assembly4. That being:
- the various pieces of the assembly (a bearing, a screw, a bracket, shaft, etc.) are required to be in a container called a Model (in the model tree of a given fcstd file). Does this mean any previously complete FreeCAD fcstd part needs to be moved into a Model container before use with an assembly?
- I don't have any problem with the local coordinate system concept. Is it required for every model and every possible constraint? Is it possible to just use the coordinate system of the part? (in the case when the parts coordinate system is sufficient).
- What are the long term plans for assembly in FreeCAD? Seems having competing workbenches will further confuse new users as they already get confused between Part WB, Part Design WB, Draft WB, etc. Is there any thought to converging on one assembly modelling process? (i.e. A2Plus doesn't need the user to add a Model container or LCS)
- Is there a use case for different assembly modeling workbenches?
Note: this is just me musing.

And wondering where to focus learning.
And BTW: Assembly4 is great work!

Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."