I would follow the lines of the sink.

Sinks usually come with a template for the counter cut.

It seems to me that if the sink's corners are rounded at the top, and the quartz is cut with 90 degree corners, a bit of the sink flange will show.

Do you just prefer right angles? Maybe look for a sink designed for that.

Thanks! I added the Amazon picture. It is a pretty slight angle that I can live with I guess. I didn’t want to spend more on a sink to get true 90 degree corners and this one was a pretty close compromise.

Installation manuals for all stone requires that inside corners MUST be radiused, or the warranty is void. 90 corners create a stress point that will eventually crack.

Thank you GreenDesigns! That’s what I needed to know :)

You are describing a negative sink reveal; I don't recommend it. Have your cutout reflect a slight positive reveal and strap, not clip or block, your sink in place please.