I'm pretty isolated in this opinion, but of the coop or run does not stink it should be clean enough. That basically means is stays dry. Dry poop does not hurt anything as long as it stays dry. When it gets wet for a couple of days it can stink really badly and harbor diseases. If it gets wet from water somehow or if it builds up too thick it needs to be managed. It needs to be managed before you get to that point.
Give them plenty of room, coop and run. If I overcrowd mine I get more behavior problems, I have to work harder, and I have less flexibility to deal with issues. Instead of asking how many chickens can I shoehorn into this tiny space think how many chickens you want and how can I give them more than enough room.
Make it convenient to you. The chickens can adapt. If it is a walk-in you need to be able to work in there without bumping into things. If it is not walk-in, you need to be able to reach every part inside.
Lots of different ways to water them. How is not that important, other than make it convenient to you. What is important is that the water be clean. If poop or trash stays in it for more than a day it can be unhealthy, bad microbes can multiply. Don't let mosquitoes breed in the water.
Again lots of different ways where the exact way is unimportant. Try to keep the feed fresh and clean.
Clean and do not let them run out.
Something age appropriate that gives a balanced diet. Balanced in all nutrients, not just give them all the protein you can get them to eat. You can get some really strong opinions on this (all these topics actually). My opinion (again a minority opinion) is that you don't
need to give them supplements unless you see a deficiency. They do not
need a high protein diet unless you are raising them for show or meat. As long as you don't get ridiculous in how much you give them no harm is done. They just don't need it.
Keeping them cool in the summer, and hot in the winter.
I do not try to keep my birds cool or warm. I try to let them handle that, like the wild birds that live where you do. For cooling I give them lots of water, shade, and good ventilation. For warm I give them enough ventilation to remove moist air and a way to avoid direct wind. I don't know where you are, if you put that information in your profile it is always available to us. If your climate is brutally hot or cold you might need to do more, but this covers the majority of us.
Caring for them while you are away
I pay someone to come in twice a day for food, water, to collect eggs, and open and shut the pop door for predator protection.
Making hens lay in one spot.
I have the nests open a week before they start to lay so they consider them as possible nest sites. I keep a fake egg (I use a golf ball) in each nest to encourage them. This does not always work but it helps.
The only effective way is to have barriers that they cannot get across. Anything else is a risk.
Introducing them to another flock.
Pass. This is worth a book on its own.
Lots of different details but if you want her to hatch eggs and raise chicks give her fertile eggs, all started under her at the same time. If you don't want her to hatch, break her from being broody.
I know, no real detail here. You would be better off starting a thread on any one of these topics, telling us your location, your goals, and your flock make-up to get specific suggestions. But expect different recommendations because so many different things work for these things and we all have our own opinions and experiences.