New to Skrimps

So I've been lurking for a while looking at everyone's hilarious and cute shrimp for a while. I finally got a few for my tank, a 29 gallon with plants, lava rocks, and a driftwood "stump". I got 4 blue velvets. I just have a few questions.

1. Can they over eat algae? I have a good bit of algae built up on my plants and I'm worried they are gonna pop!

2. I want so many more. If my aquarium is planted and has plenty of rocks and wood in it for hiding places, will I have baby shrimp even if there are also 9 neon tetras in the tank?

Thanks!