None of the lower trails are poison oak free, relatively or otherwise.
If you are at low altitude, ie, the pre Redwood Camp/ Sykes portion of the Pine Ridge trail, then you are hiking in poison oak. The trails are fairly wide so if you pay attention you can avoid brushing into it, but it's not poison oak free.
Barlow is a big camp, with big spots, a very nice place.
See ventana wild trail conditions for a per trail overview/report.
Basically you have to decide which part of Big Sur you are going to go into, if you start at China Camp, there is not a lot of poison oak along the pine ridge trail up there, but I don't know about the degree of poison oak on those upper trails right now, or going to the camps up there. There are not many open loops at this point, trail damage apparently still not fully cleared up by the volunteer trail maintainers.
If you start at Botcher's Gap, you will be in poison oak at the start of the climb, but it will grow to be less and less by the time you get up to the ridges, which are beautiful. Depends on what a day's walk means to you, of course. That's a very steep trail. Pine Camp is big if I remember right, or at least has big flat spots. Most of the places up there are pretty big, even Lone Pine. That's a steep climb, and going down is a knee destroyer, it's an old jeep road, ie, graded for a jeep, not human legs like most trails.
Most of the trail reports don't talk about poison oak levels since it's pretty much a constant anywhere below 4000 feet, much lighter at higher altitudes.
Remember to watch for the ticks too, they have Lyme disease, and are very small, sesame seed size or less, depending on season. Think about using permethrin on your clothes and following all anti tick advice to the letter.
To properly answer you have to define what mileage you can do per day, if you are willing to hike in the dark, and other things like that. Creek crossings are not currently an issue at this time of year, all of pine ridge last month was crossable without even touching water, but after the first big rains, you'll need to bring some kind of water shoe to safely cross them, but that's not a big deal, they aren't that big, and there aren't that many along Pine Ridge. I don't know about the Southern Trails, it's been a long time since I've been on them, the Northern ones, like up from Botchers, dont' cross anything you can't cross with a jump.
I would skip the Ventana camp if I were you, Barlow is only about 45 minutes more total (you hit Terrace Creek roughly the same time you would have hit Ventana, and Barlow is only about 45 very easy minutes from Terrace), and you don't have to wake up and climb back up the 1 mile you climbed down, also Barlow tends to have fewer people, and less weird stuff, Ventana is too close to the trailhead for my taste.
Another option is to go from China Camp and head to one of the central sites, before Pine Ridge, which doesn't really have good spots on it for two tents, you can get by, but if anyone else is there you'll be unhappy. Just remember the loops are all currently non functional, ie, missing a mile here and there, at least so I understand.
Update: skip the trip this weekend, weather: rain likely this weekend.
Unless you like that type of weather, if you do, give me a call next trip, heh...