I didn't carry an umbrella, but I did hike with a person who did - her complaint was it was just too windy in Southern California to be that effective. Trust me, there were moments when I was quite jealous of the dang thing, no matter how awkward it seemed to hike with it. But for every few hours were there was no breeze and it was of benefit, there were far more hours and days when the umbrella seemed more like a nuisance, always shifting under than fairly constant winds of the Southern California.
I think finding shade or improvising shade with a ground sheet a far more effective solution. It is hard to say what kind of weather you may encounter in SoCal, it really can vary. But when it got up to or over 100 degrees, there were times when it made more sense to get up before sunrise and hike until 11 a.m. or noon, then take a break until 4, and then hike again till 8 or 9 p.m. We'd try to hike to a good water spot and then find some shade, drink or fill, take nap, eat some food, and then head out after it began to cool down a bit. Others hiked right through it, no problem. The heat beat me down pretty good.
On the charger front, many people carried them, many complained about them, and I think more often than not, they ended up in a bounce box or sent back home. They'd just charge in town. Some would carry these instant charging devices made by Duracell or other companies - I don't know how well they worked.
Finally, gear seems to be a big part of the conversation for a while - say, the first 500 miles or so then nobody really cares anymore - you find what works and what doesn't. By then, you've hit your stride and you can make must about anything work.
The thing that gets kind of lost in the entire trip is time. Tthe first 250 miles really kicked my butt and felt like it took forever to complete. The next 450 or so took a long while, then your reach the Sierras and life couldn't be better. After that, time and miles begin to race along. By the time you reach Oregon, well, you have only 1,000 miles left and you are practically done.
John hiked the PCT when, well, the number of people attempting it probably didn't total more than a few dozen or so. I have a ton of respect for that - meeting people who hiked it in the mid 1970s and early 1980s when there was much heavier gear, fewer resources and no real trail guides - those people did it the hard way. Very cool.