In my wig-newb opinion you're going to have to choose between a short wig with add-ons or a long wig that you can heavily alter into this. If you go short I still don't think the Chibi is a good choice; the buns on that cosplayer you linked don't look "built-in," and I can't imagine how you'd build a bun up and of a thick head of hair underneath it.
If you go long I'd think either the Eowyn or Venus (or maybe the Natasha?) would work, depending on how long those tails need to be. That way the tails are essentially built-in, and you can use the extra hair to make the buns (which I'd imagine you would build like any bun/odango clip-on). You could also use some of the extra length to tease up the back a bit like the cosplayer you linked so it's fuller.
Going short I think will be trickier 'cuz it'll be harder to get all that bulk in the back. I'd look at maybe the Greta 'cuz you can straighten it for more length and then tease that in the back. You could then add the buns as clip-ons and use long wefts for the tails in the front.
Personally I think starting with the longer wig would make more sense, but like I said this is kind of all theorizing from me, I haven't done a wig with this much clipping and moving of hair before.
KuroNekoCon- '11 : Radcon-'12 : Akicon-'13 : Sakuracon-'13-'18 : PAX West-'11-'18 : Rainfurrest-'15 : ChibiChibiCon-'17-'18 : RenCon '17
Princess Peach-New Donk City (Super Mario Odyssey)