I've owned E26, 2x E27, and had a few goes on an E27z.
E26- zero tail but often sold with the extra counterwight which you will need for Arb work. 25hp Kubota engine, auto idle. Usually had the rocker controls for aux and often had the boom offset on the left lever- easy to fit a divertor for rotate. Plastic covers so often looks cleaner than E27/z models that have gotten rusty.
E27- replacement for the E26. 25hp Kubota engine. Heavy counterweight now integrated into the frame (big plate of steel underneath) Auto idle. As with E26 usually had fingertip controls and usually sold from new with the second aux divertor fitted. It's not zero tail but is very much compact radius. Nowhere near the arse of a Kubota KX27 but extremely stable- a very good compromise.
E27z. Introduced alongside the E27 as a cheaper 'hire' grade machine. 20hp Kubota engine (Yanmar on the newest models). Manual throttle control. Zero tail. Standard spec with pedals for aux and boom swing, often bought as 'arb spec' with rollers and a divert kitted by people trying to save a couple of grand. Doesn't make nearly as good an Arb digger as the E27. Zero tail makes it very noddy, it's cheaper inside the cab, and the missing 5hp from the engine means that it's a good deal slower overall, which is not what you want for repetetive Arb work.
The options for the fingertip controls on the aux and the boom slew are called 'comfort package'. Dealers usually spec them on the E27 but often not on the E27z which is sold at a lower price point. The second package for the rotate is called Aux2 and consists of the divertor from the boom slew plus the pipework down the arm. The pipework and divertor is relatively easy to retrofit, but retrofitting the joystick levers is not cost effective as lots of the valve block would need to be replaced too.
As an aside, the E26 was re-designed somewhat and is still a current model, it has a very distinctive boom which the cylinder sits inside. They don't sell much in the UK, I've only ever seen one in the flesh at the dealers. I don't know much about this updated model but I'd guess they sit somewhere between the E27 and the E27z. It seems very much superflous. It only has the 20hp engine.