I use the Arca RM3di with a Leaf 50 back. I was advised not to go above 60 because higher pixel counts apparently are problematic. The viewfinder is a waste of money in my experience. I use an iPhone with the Alpa app, and often just rely on LiveView.
I have the e-cloud, but have stopped using it. I find it is easy enough to dial in proper focus using LiveView at 100% and wide open aperture. For landscapes, this works fine. For closer objects, I use the distance cards provided with each lens to get to the proper area on the focus dial and then go to LiveView. I get about 90 to 120 minutes (cold weather) out of a battery this way, and I carry three or four batteries. Shot count is what really matters, and when it is warm, I find I only need one or at most two batteries to get me through a five or six hour day--maybe a 150 exposures, often involved stitched images.
The system isn't the easiest to travel with if you are using longer lenses because extension tubes are required that making packing the camera in a carry-on case that fits under the seat difficult. If you are not using longer lenses, the camera packs down rather nicely.
Be prepared to to use the LCC opaque card, which does add time to the process, but it is essential with camera movements. This will also require additional work in CaptureOne, but not a big deal.
My biggest complaint with the camera is the lenses, which I don't find to be mechanically reliable--Schneider (4) and Rodenstock (1). My 43 isn't working right now--second time. Three of the others have stopped working for awhile, and then started working. On some occasions, the shutters wouldn't close once triggered, and on others the shutters wouldn't open. This may be cold weather. Currently the other ones have been working, but I am now reluctant to photograph when it is real cold out.
Other than that, I love the camera.
If you go with the Arca, I would use screw in cables rather than the magnetic ones. People report different experiences, but in my experience, the magnets are not strong enough and occasionally pop out.
One word of caution, which the other more technically inclined can comment on or correct. As I understand it, the lenses use Copal shutters, and that company apparently isn't making those parts anymore. As I understand it, the lens companies are coming out with electronic shutters that can be retrofitted to the existing lenses. I took a quick look at that as an option--it looked expensive and complicated. So be before buying into one of these systems, I would address long-term viability. At some point the shutters will fail.