Recuperation is a nice but not mandatory thing to have. The (now discontinued) BionX motors used to have it i.e. and experience showed that in mixed terrain the gain was about 10-14% of reach in practice. Not too impressive, especially today with larger batteries being available and at lower prices than a couple of years ago.
In the flat the gain is obviously even less than that but there's another nice feature to the recuperation there: You can use it as a brake: As typically switching to recuperation is triggered by the brake lever and starts slightly before the actual brake starts to work you can break w/o using the bike brake and safe on wear there while having a constant, predefined amount of brake power. Equivalent to a ******er brake in big tucks or busses. Very comfy in the city with traffic lights, especially as the recuperation is configurable.
Recuperation only works with direct drives and is typically only implemented with rear wheel drives. Thus it is not very common today, with geared and non-geared front wheel drives being the common cheap upgrade solution for non-ebikes, non-direct rear wheel drives being a almost as cheap but less common alternative and mid-drives (where recuperation is not possible currently) becoming more and more the standard with factory e-bikes. And as recuperation adds to the cost of the drive and retrofit kits are mainly sold by their price it becomes even less common.

However: This has only little to do with the Vello. The Vello is using the Zehus motor. It has been on the market for a while already and - while being a bit exotic - it is used by a number of manufacturers and a clever design. While it is a rear wheel direct drive and offers recuperation there are some features that make it different: For one everything is within the rear hub. Motor, controller, batteries. This gives it a very clean look as there are no cables to go anywhere and no buttons or other elements anywhere. It also would make retrofitting a snap if there was a retrofitting kit available (which is not, they only sell to bike manufacturers).
With this concept obviously only a small battery is possible which obviously limits the reach of the motor. Therefore they implemented various power modes including one for recuperation and one for charging while pedaling. Again these are configurable as far as I know regarding their intensity. When I test rode a prototype of the vello about two years ago it was in charging mode, possibly set to a quite high intensity, and it felt like riding uphill in the flat. It was ony a very short ride, so not much to judge from there. I did not dive into the concept further but would assume that as you can configure the motor including the parameters for charging mode and recuperation using bluetooth via a mobile phone it could possibly be useful sometimes, i.e. by charging the battery in the flat in expectation of a steep hill a bit later on the route. So in theory this makes the bike offer an unlimited reach with electric support - which is in my eyes only very theoretical. A least this is what I got without diving deeper into it.

Other than that you can charge it via a wall plug wich connects to an electric connector on the axle of the rear wheel. W/o any recuperation or charging mode I'd - based on the size of the battery - assume that the bike would have roughly 25-40km of reach with electric support, depending on the support level. However: No practical experience of mine. So not so much a touring bike but sufficient for commuting and hopping around in the city. Which seems exactly what this bike is made for.

In general it is a nice bike but not my cup of tea. Regarding the motor part I especially do not totally buy into the concept of having to use a mobile phone for any configuration and change of modes. The motor steps in automatically (based on the mode preset), but any change of the mode needs the mobile and based on my experience with electric bikes and how often I change modes while riding I consider this very inconvenient. Would however need testing before coming to a final conclusion.

Worth mentioning is that with the Zehus motor - at least with the current version - there's no gearing available, neither internally in the hub nor via derailleur. Vello do offer a Schlumpf Drive in the bottom bracket, offering two gears which as usual comes at a price in terms of money and weight. One could possibly also use an Efneo drive with three gears in the bottom bracket.

There is as to my knowledge at the moment just one rear wheel motor on the market that offers internal hub gears but obviously does have batter and controller etc. outside the hub. There used to be a three-speed one from BionX but this is gone for quite a while already and also had the need for external parts.

Regarding the vello there's already a thread in this forum and also the kickstarter campaign page for the vello offers information and links to further information via the comments.