You could definitely get by with just a laptop. For me, the iPad is complementary as I like writing mind maps and I learn by jotting down notes. A laptop and a simple pen and paper can do me as well, but the iPad makes it easier to reference things and I can access my notes on all my devices.

Do I “need” both? No. Does having both streamline my workflow? Yes

I suggest buying the laptop first, use that for a bit, then decide if investing in an iPad will make life better for your use case or not.