What about sizing? I am 180 cm, 90 cm inseam (long legs, short torso, long arms)...I ride an Orbea Occam size L (reach is 470mm). I think the best option on the Vitus for me is size Large, but I fear that the wheelbase of the bike might be too long (I ride alpine trails that are usually quite slow and require above average technical skills).Welcome !!
1: Spare batteries don't seem easy to obtain at the moment. They should be in theory as they're a standard bafang unit, but I'm not aware of anyone who's bought one.
2: They're all owned by Signa Sports which is part of Signa Group which is owned by a low life thieving scum bag called Rene Benko who ultimately will have ended up destroying the lives of thousands in these businesses and all the connected businesses. Hopefully a few will come out of the other side, though most have had any cash siphoned off and the whole thing is a mess and will end up with everyone fighting everyone to try and get anything back. With luck, some of the smaller elements, such as Vitus, will have been too small to bother using as cash cows and will come out of the other side as viable enterprises.
3: The motor has a torque sensor built in, it measures the torque you put in then applies a relevant amount of assistance. Your understanding is more or less correct, though I wouldn't try and interpret the numbers too much. Initially, eco might seem like too much because you're not used to any assistance. After a couple of weeks you'll have adapted and will have a higher average speed and it will feel fine. You'll probably start using the other modes and your riding style will evolve and adapt to different terrains, so going up might also become fun like going down (though obviously not quite the same).
4: You can in theory tune the motor with Go+ (with an upgraded display) or some other tools if you buy a "box" - there's a thread on bafang tuning. In reality, you probably won't need to. There are many other factors like rider weight, speed, type of terrain and especially vertical meters climbed. You can also turn it to no assistance if you feel fit/strong/crazy. Assistance will also stop at 25kph, so another way to get more range is to push past that. In the middle assist mode you should easily get 1500+ meters climbing. In Eco 2000 to 2500m. With any e-bike if you power off or "ride the wave" at the cut off point you can get lots more, you just need to pace yourself and not go crazy and tire yourself out on the descents too. It's physically exhausting though. An example on a 630wh Bosch Bike :
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lots of up and downs rather than a nice mountain :-(
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It's a great bike. Ultimately, it's unlikely you'll need to buy parts from Vitus as it's all pretty solid. Bearings are standard and listed in the tech thread so easily obtainable.
In terms of bikes, I have a Cannondale Scalpel HT (11 kg hardtail, 100 mm fork) and, as I said, an Orbea Occam (15kg, 150mm suspension front and rear, Maxxis Assegai 2.5 front, Maxxis Dissector 2.4 rear). The Cannondale is super fast uphill, the Orbea is very slow uphill but capable downhill. I guess the Vitus in 170 front / 160 rear configuration with 2.6" tires front and rear would be a great way to ride the same trails I do with the Occam, the only difference is that I would be able to do many more descents.