Deep lake... leans toward bigger diameter net with more weight.
But being new, as you write, I’d recommend an eight footer, maybe ten footer, with heavy weights and some YouTube and on the water practice.
Edit: pick a reasonable mesh size. If 1/2” will work, don’t get 3/8”.... the larger the mesh for diameter and weight, the faster the net will sink. Catching bait in deep water , especially bait holding deep, requires a fast sinking net (with the largest diameter you can actually get to expand when you throw it.)