If you're interested in having a flash be a part of your camera system, the X-E4 does not have a built-in flash, whereas the X-S10 and the X-T30 II do. When it comes to photography, and you start growing into it, the built-in flash could have a better position because it's straight in line (which gives that deer-in-headlights look at times). The built-in flash also requires an output power to sustain full-on productions, event photography, etc.
Button & Dial Layout
Depending on the type of photography you want to do and the shooting experience you intend, the button layouts between these three are very different.
All three are rangefinder-style bodies, which will have your viewfinder off to the side and a minimal button layout — a dedicated shutter speed dial and faithful exposure compensation dial. This layout is excellent for photography, especially for those who are starting to understand camera settings. However, it is limited to one front command dial and no rear command dial. Thus, reduced dials might be a downside for photographers who prefer total manual exposure.
If you require more manual experience, the X-T30 II will be the better bet. It has a dedicated shutter speed dial, an exposure compensation dial, an aperture dial with the lens, and a front command dial that maps an altering ISO.
The X-T30 II also offers separate buttons for autoexposure and autofocus locks, making it the best photography-oriented control layout of these three cameras.
The final consideration is battery life, and while they offer the same battery, they measure various efficacies. Under one battery — the X-E4 has an estimated 460 frames, the X-T30 II offers 390 frames, and the X-S10 does the worst at 325 shots under a single charge.
I recommend that everyone obtain one to two extra batteries for their Fujifilm cameras to photograph all day. Furthermore, all three cameras can be charged via USB-C.