traingang

What's your issue with the weight? The Decathlon and the Cube come in at give or take a kg difference depending on trim level and obviously whatever accesories you choose to throw on it, only the estarli comes out at about maybe 5kg less, but it's still 28kg which doesn't exactly make for a pleasant experience trying to carry it up some stairs or whatever. For the riding it's not going to make a noticeable difference, especially once you chuck you and 50kg of extra weight on it.

The cube also specifies a maximum rider weight of 100kg so I'd make sure you (and possibly a backpack) is within that.

Am I barking up the right tree by looking at what's available locally for servicing/accessories?

Depends on how good you are at servicing a bicycle. Longtails don't really have anything out of the ordinary that you wouldn't find on a normal bicycle, like fancy steering linkage or whatever, because they are basically a normal bicycle except long. If you wanna replace a chain you just buy two and link them up or buy one of sufficient length. Replacing brake lines or hydraulic fluid is just the normal way, except longer and more. I'd argue most bike shops are well capable of all of this, allthough I'd check with one if they repair models not sold because some of them are annoying about it.

That leaves the motors. The Cube and Estarli have mid engines, which do need servicing, which I assume your bike shop can do. The Decathlon one runs a rear wheel hub engine which do not need servicing because they're sealed and enclosed brushless motors which you're nobodies is supposed to open. They work until either water does get into them or I guess whatever bearings they got running in there conk out, which unless you got a faulty modell is gonna be like a decade or so unless you're planning to tour de france the thing a lot. If it does break the replacement is just a new rear wheel with hub motor. Decathlon calls it a BTWIN engine which I'd bet money on is just a rebadged Bafang, like how they're BTWIN Gear and Brake components are just Microshift. If you can connect up some wires you could also probably do this yourself, otherwise this isn't really work that a halfway competent bike shop couldn't do but again, check if they would.

Are there any good cheaper chinese options that are just as good as the three options I've narrowed down to? (I've seen Fiido longtails but not many reviews for them)

Not as of yet. Drivetrain and brakes and such we're there, but it seems they're just entering the market for "normal" bicycles that aren't comparatively cheap carbon bikes with really questionable QA now, I don't think there's cargo bikes of any colour there yet. It's mostly still department store / amazon stuff which cheap mystery components and trispoke wheels and such. I wouldn't exactly imagine the frames break in half but I would imagine you'd end up replacing most components very shortly. Here's hoping it improves.

Fiido once had to recall their X Folding Bike because for some idiotic reason they figured magnesium was a good choice of material here and it snapped in half a lot. There's also the issue of the seatpost being the battery and you were able to put it down so deep through the seatpost tube it came out of the other end and was at risk of scraping. First one was definitely fixed, I'd assume they also fixed the second issue in their V2, but it's still out of magnesium. I'd put this down to harebrained bullshit about reinventing the wheel, their longtails are aluminium frames which is tried and true enough I wouldn't worry about that one.