B7HS is a little cold when you consider a B5HS is in the same heat range as the Chinese plug. Yes, it will work but will be more prone to fouling due to not enough heat. Colder plugs are used when you raise the compression by milling the head or going to the Manic Mechanic heads or Puch heads which also raise the compression.
BR5HIX is the NGK Irridum plug, kinda expensive but I really liked mine and got another for my Morini.