About to dive in: Is X-E3 + 35mm f1.4 a good 'single prime' camera choice?

I think that's a good plan for a number of reasons.  As a rangefinder style shooter I use the XP2 but I understand that the XE operates similarly, for less.

The 35mm is pretty much what was considered "normal" for many years and is a good all around choice.

Also...the 35mm f1.4 is a sweet lens.  I own one and highly recommend it.  The f2 model seems to offer more for less but it really does not.

The Fuji f2 lenses are software corrected, with the possible exception of the 23mm f2 whereas their faster cousins are optically corrected.  This shows up in a couple of ways, first the output is cropped somewhat (perhaps not a big deal) and also RAW converters have more  difficulty successfully converting their output.  There has been a lot of chatter about waxy skin, artifacts and watercolor grass with Fuji RAW files.  Some of this was due to the learning process for software developers with the X Trans sensor.  However a large contributor to this issue was the software distortion correction (SDC) and the extra burden that it places on the RAW conversion software.

The 35f2, even with SDC is weaker in the corners than the f1.4.  The 1.4 is a touch less contrasty and so some claim the f2 to be the sharper lens.  A slight post processing contrast adjustment shows that claim to be false.

The F2 is the less expensive choice though and it's still an excellent lens.  I'm just pointing out that most often better cost more.