Towing in the mountains: the routes near big bear lake

I towed boats from Temecula to Big Bear for years. Always used the 38. Recently drove up to the park you are talking about with just our F350. Used 18. Decided the campground wasn’t worth it. Very tight for our 35’ fifth wheel. Most of 18 is 4 lane. Most of 38 isn’t. I’d go 18.
Either way, the access road to the campground is tricky. As I remember, turning off the 18, you need to make an immediate right. We missed it. Had to go a ways into town just to turn our truck around.