Hello Vagrant core is the open source program.
It works fine for boxes, and the overall user experience is quite easy.
Hashicorp only provides the boxes under hashicorp organization in atlas, so in this case the box you are having issues is not a hashicorp box.
having said that, one option is to contact the people that has build the box/project you are using as they could assist better.
To answer your question, yes you need both products plugin + workstation. I think you can download workstation as 30 day trial, and the plugin have a 30 day refund period, so you can evaluate and get a refund.
Depending on the box/boxes you want to use, not all of them are in vmware version, so please check if the box you want use exists on VMWare.
On top of all of this, what about you building your own box?
Alvaro