We can see the problems that arise when trying to discuss these "end-fed" thingies
There's so many variations, lots of hodge-podge and rules-of-thumb, but very little actual design.
The EARCHI type "designs" are a mixed blessing - they're probably responsible for getting thousands of hams out into the field and up at the summits for remote activation with easy to set up equipment!. OTH, the hodge-podge "design" also has lots of folks thinking that being able to TUNE, and radiating EFFICIENTLY, are the same thing Of course, they are not the same thing
Unfortunately with these rules-of-thumb: sometimes we use a "counterpoise", sometimes we don't need a counterpoise (which of course isn't true), sometimes we use the coax as the counterpoise, sometimes use a 24 ft wire, no, sometimes we use a 37 ft wire....etc.... This only means that's the "designers" didn't really have a good handle on how these systems work.
It's also why so many hams are sour on the lower bands. One is virtually guaranteed to be badly INefficient on the lowest band or 2 that can be tuned with one of the typical EARCHI type end-fed setups.
There's no magic setup - on the lower bands, there's no escaping that a "radiator" wire needs a good RADIAL system when it's length starts becoming significantly less than 3/8 wavelength or so.
By contrast, many "end-fed" type implementations can be thought of as a "radiator" wire with a single short radial - IOW horribly inefficient, especially on the lower bands.
While an UNUN is a good strategy for the high bands, another mistake often made is to use the UNUN on the lowest band where a loading coil is what is needed. Almost counter-intuitively, the fact that some of these hodge-podge end-feds can be MATHCHED on the lower bands necessarily MEANS that they are horribly INefficient.
The point is - before bounding off into end-fed-world, first get back to some basics, and realize that's there a bit more to putting out a good signal than just getting the Reflect Power Needle to read zero. Once we have the antenna actually putting out a good signal, then we can worry about those few dB lost in a coax cable.