I've done this route several times. It's very pleasant.
1) Google maps is showing the Trail pass trail, which is less travelled than the Cottonwood Pass trail. Gmap 4 is soooooo much better than Google maps: https://mappingsupport.com/p/gmap4.php?ll=36.452398,-118.191038&z=15&t=t4 shows the cottonwood pass trail clearly. If you're not a Gmap4 user then it's easy - just note that you can change the type of map on the top left, some of my links below are satellite vs topo.
2) Early season/high snow/after a massive rain storm then Rock Creek can be tricky, but that's highly unlikely in July this year. My 7 yr old son did it a few yrs ago and was barely knee deep.
3) Given the altitude (and time taken to get to the trailhead unless you camp there the previous night) I think Chicken Spring Lake is a very sensible first night. If you want to push on, then one option is to take the route that goes via Lower Soldier Lake and stop there, or a mile later at Rock Creek lake. That would make it about 10 miles.
4) Pre-summit I nearly always camp at the junction of the JMT and MMWT. It's spectacular. https://mappingsupport.com/p/gmap4.php?ll=36.561592,-118.293280&z=20&t=s This is a dry camp, so I cook dinner at a spring beyond the tarns here: https://mappingsupport.com/p/gmap4.php?ll=36.566647,-118.303155&z=20&t=s There's also some good camp spots on the slabs just N of that spot, or here a few hundred feet further North: https://mappingsupport.com/p/gmap4.php?ll=36.565373,-118.301859&z=20&t=s
5) I take 3-4L/person from the spring to the summit and down, but that includes a dry camp for the night, and I always have too much water. Camping so high, and starting early means its _cold_ first thing, so I drink very little on my summit morning.
6) You can have a fire if you camp at the final Rock Creek crossing, that's about the only place I'm aware of that permits them.
