I think either plan is great although the one that includes Lake Tahoe will mean extra driving. If you have a keen interest in seeing the giant sequoia trees including the world's largest tree, then SEKI is the best place to see them. If you have a keen interest to see the large, beautiful Lake Tahoe, then Plan B is better. Either plan is fine and mainly a matter of personal taste as to what interests you the most. I probably would not try to do all 4 (SF, Yosemite, SEKI, Lake Tahoe) in one trip unless you had a couple more days than you have.
With either plan, I would be worried, though, about catching the flight out of SFO. For my own trip I would choose to spend the final night close to SFO and not risk driving a long way and trying to catch a flight the same day. From Wuksachi Lodge to SFO will be at least 5 hours of driving without including stops. I would not want the occasional vagaries of driving a substantial distance to possibly affect whether I would make it to the airport on time. I would be likely to subtract a night from the San Francisco time so that I could add a night near SFO before the flight home. However that's being cautious, and in theory, you could carry out your plan A as is, provided you got a very early start that last morning and drove to SFO basically nonstop.
And driving from South Lake Tahoe to catch a flight at SFO the same day seems a little dicey as well. If you were flying home out of Reno it would be much easier. If you were doing this whole trip flying into and out of Fresno it would be easy to get from Wuksachi Lodge to the Fresno airport in maybe 2 hours. But to get to SFO from either of these starting points and catch a plane that leaves at 1:30 seems a little bit chancy to me; I personally wouldn't take the chance myself.
If you do go with Plan B to see Lake Tahoe, then I would probably drop SEKI completely from the trip. You could still see some giant sequoia trees at the Mariposa Grove in Yosemite. SEKI has more of the giant sequoia trees, including the world's largest tree by volume, but if your reason to go to SEKI is simply to see some examples of giant sequoias, that need can be filled at the Mariposa Grove in Yosemite, making SEKI unnecessary, although the SEKI region does have the largest number and greatest concentration of those trees.
The weather in California in October is typically clear, sunny, dry and warm in the daytime. This usually holds until the end of October as well. The first winter-type storm usually doesn't arrive until the end of October or early November. It is possible, especially in a so-called "El Niño" year, that a winter-type storm can come through in October, and on October 17, 2004 a snow storm did hit Yosemite, though it is unusual for one to come that early. Most areas of California see clear, dry, crisp air in October, and if a "Santa Ana" condition is prevailing (where a huge high-pressure air mass sits over the entire southwestern U.S.) it can even be surprisingly warm at that time.
I think you will likely find clear, sunny, warm days in late October, but the nights will cool down dramatically. We camped in SEKI in mid-October once and it was 70 for the daytime high but 30 for the nighttime low. But as soon as the sun comes up it warms up quickly. If Tioga Road in Yosemite is open when you are there, you should drive it, all the way to Tuolumne Meadows and back, as it is a spectacular drive, the highest public road in California. Services along that road may have already shut down for the year even if the road is still open. So gas up well at the gas station at Crane Flat in Yosemite before making the Tioga Road drive. And, if Glacier Point Road is still open, drive up there too.
Edited: 12 years ago