Tubeless sealing:
Nail? Maybe, maybe not. Staple, highly likely.

One thing that isn't clear from your post is what size tires. Wide mountain bike tires running at 30psi and below will seal better than road tubeless at 60+ psi. For example, a nail hole might seal in a mountain bike tire, but not a narrower road tubeless tire. This is basically a function of the higher pressure for road tires. The advantage of tubeless is that you can run very low pressure with good ride quality.