AlexW wrote:

As I have done drains/downpipes with grinders ... does it work well?

I think so; it won't 'grab' the material and bend or crack it. It
shreds it into fine swarf, Some of the swarf melts and sticks to the
sheet along the edges of the cut, but comes away easily.

What blade type is best?

I just used whatever was in the grinder. I think it was a masonry disc
last time, but I don't think it matters much.