I have done trips #1 & #2.
The Ohlone Trail is suprisingly remote, given its location, which surprised me since it just in my "backyard".
The big downer is that a good portion of it is in the flight path of planes going into SFO....so at one point, we had a plane over us every 15 minutes or so.
This time of the year would be better than in the fall when I did it...things would be green and you would have water.
There is a fair amount of elevation loss/gain and with the rains, I would tell you to expect lots of mud. The soil is clay, so you will have clumps on your shoes to knock off from time to time.
If you do this, get dropped off at the Sunol side and finish at the Pleasanton/Livermore side.
It is very steep coming out of the Pleasanton/Livermore side, plus, the book that I have said that there can be crime issues with cars left at the Sunol side.
If you want more details, let me know and I can look stuff up in my book, "Hiking and Backpacking the Bay Area."
The Ohlone trail is about large rolling hills with a few trees....decending into a deep gully near the end with a stream or two. Overall, it is a pretty trip, but I would not do it in the late Spring or Summer...very hot, dusty, and limited water.
#2 I did this one out of Big Basin and was my 1st solo trip. A very pretty hike, cool weather with lots of trees, and you will occasionally hear the sound of cars. The annoying part was when the trail was close to the road, there was garbage dumped onto the trail or near it. Much more scenic than the Ohlone.
I did it from Big Basin to the Ocean and then yo-yo'ed back to my car at Big Basin and then headed North to the top of the Skyline trail.
I went in Oct and had limited water on the Northern part. The only water was at one of the established camps.
Again, I can look this up for you if you want and provide the information.
Between the two, if you are looking for solitude, do the Ohlone...if you want a big variety of scenery, the Skyline to the Sea.
I have not done Henry Coe, but there is supposed to be a 50 mile loop that I am interested in doing.
Anyway, hope that this helps.
P.S. Other places to go are in the Santa Cruz Mountains....Castle Rock State Park and the large number of small parks around it. Castle Rock is not too far from the top of the Skyline trail.