Use as many as you want. Just add up the total Watts and stay under 2,000, the way you plan to.

Since you plan to be by yourself or have one other shooter you won't need to light up the water all around the boat. You can probably get by with 6 lights, but then you can use brighter bulbs. I find that many boats do great with 4 lights up front, and 2 down the left side. Not many right handed shooters take shots to the right side of the boat. Use 8 if you want to go all around, or 6 for just the front and 1 side.

Don't overload the cheap generators. They have durability issues and will not run for more than a few outings at 100%. Better to buy a bigger genny, or use fewer total Watts (80% of rating).