I recently traded in all of my Canon FF gear (I shot 5D, II, III, IV over the years) and switched to the Fujifilm world and an X-H1. In terms of exposure, I suppose there are two general aspects to consider - 1) exposing for the JPEG and, 2) exposing for the raw file. I shot pretty much 99.9% raw with the Canon, and there is no reason not to continue shooting raw with the X-H1, so this observation about exposure on the X-H1 is from the perspective of exposing for the raw file.
With the Canon, and more specifically the 5DIII and 5DIV, I metered with the spot meter for the lightest highlight in which I wanted to retain detail. The reflectance spot meter in the camera and the spot meter in my Sekonic meter more or less produced a similar result, but I would consider the Sekonic spot the reference. After shooting many different scenes under daylight (i.e., not tungsten artificial light) and analyzing the raw files using Raw Digger, I concluded that I was able to expose +3EV from the metered reading and retain highlight detail without clipping the raw data (specular highlights aside). Acquiring an image was then as simple as metering the desired highlight and adding three stops of exposure. This technique gave me the optimal sensor saturation (i.e., "ETTR") for raw conversion. If some clipping did occur, it occurred in the green channel and the red and blue channels, which are typically underexposed by 1 to 1.5 stop or so in daylight, were still intact for highlight reconstruction, given that the raw converter I used did reconstruction from the intact channels.
The X-H1 and the X-Trans sensor is not much different in terms of how I have been approaching working out exposure. I have found that I can expose at least 3EV above the metered highlight reading - depending upon which raw converter I use, and assuming that the brightest highlights are neutral (like fluffy white clouds), I have been able to expose almost 4EV above the metered reading and still get highlight detail (albeit partially reconstructed from the intact red and blue channels where green clipping occurred - again, this is dependent on the raw converter, and exposing based on your raw converter is probably not good exposure practice in general!).
If I were conservatively exposing and did not need to walk the ETTR tightrope, I would use the same technique as with my Canon equipment - meter the brightest highlight in which I want to maintain full detail and then add 3EV and fire away.
In terms of making this work with JPEGs, well, that would probably depend upon the scene and the camera settings. I find that Eterna with -2 highlights and -2 shadows at least opens the tonal range and renders a flatter, more log-like image that preserves as much of tonal info for the ETTR exposure. Otherwise, I would simply decide that I am shooting for JPEG only and expose in the viewfinder WYSIWYG in whatever film sim and settings I like, with some attention to the exposure indicator.
Hope this helps.
kirk
