The cave's first chamber is gigantic but there are some very tight spots further in. At the staging area, there's a simulation of the tightest point, so you could evaluate beforehand if you think you can manage it. It's about an hour tour.
A lot of their coasters have been on one train operation for a long time now. The past few times I've been, ALL of them were on one train but I haven't been this year. This hurts Time Traveler really badly IMO, you'll get in line and it won't look too bad but then realize how sloooooowwly that line moves.
Yes you will get soaked on the log flume.
No single rider lines. You can buy a Trailblazer pass that does make a big difference for some rides but I never felt it was worth the cost. However, I believe you can purchase a single use pass for $15 and I can't deny I'd be tempted for Time Traveler, especially if I hadn't ridden it before. But I genuinely love the queue music so IDK