Uni friend works on this, bunch of pretty amazing people doing real engineering here. The rest of the industry is betting on SAF as the way to green wash flight as 'green enough' for the masses so I think it's great that RR are doing this.
Incredibly similar to the roadster. Existing chassis with electric crowbarred in, but you can't argue it doesn't work. I haven't don't the math on the battery kWh (articles I read unhelpfully used the mobile phone as a unit of measure), but it all went into the same space as before.
The industry touts SAF as the way forward and hold it up as an opportunity for farmers and small holders to make money. Yet I'm pretty sure my higher geography being pretty disapproving of cash crops :-\