You'll be good. The sink rests on the countertop itself and that is where it gets support from. The flange just holds it in place from moving side to side (once you tighten the brackets under the countertop) and covers the hole you've cut in the countertop for the sink.
and you are correct about swapping hole saws for each material.
Suyneej t1_j242vdn wrote
Reply to Help drilling a hole through kitchen countertop & flange of undermount sink for a water filter by [deleted]
You'll be good. The sink rests on the countertop itself and that is where it gets support from. The flange just holds it in place from moving side to side (once you tighten the brackets under the countertop) and covers the hole you've cut in the countertop for the sink.
and you are correct about swapping hole saws for each material.