Cornish x are the way to go for max meat production.
I would go with 25 unless you are on your own. If you will not be getting any help you may want to go with a dozen or so.
If you have done this before with extra roos and familiar with the deed you will be in better shape to do 25. You may want to consider butchering them in batches to keep it manageable.
When I started I got 6 meaties from the feed store---mistake 1- They were ok, but I had not done my homework-- Mistake 2.
I also put them in with the hens I had at the time-- mistake 3. Bought feed a bag at a time--- mistake 4.
Avoided mistake 5 and built a wizbang style plucker off the bat. yes i did try to hang pluck one- only one.
Lessons learned
1. Batches of 25 are best for me- on 2 week intervals - staggers butchering.
2. Watch the weather- cold impacts development- heat is hard on longevity.
3. Buy food in bulk- eating machines.
4. Tractors are the best housing option- have enough space to move around every day or so.
5. Rig a feeding and watering system that keep your input to a minimum.
6. Scalding temp is important- lots of hot water stays at temp better.
I have posted these before, but if you have not scene take a look at the slick processing. "graphic" detail
Good luck