Throwers keep spilling items off belts
Throwers only check if there's space on a belt at the moment of throwing, so if the belt filled up more from the belt behind it between the time the item was thrown and the time it landed, the excess would spill out. If a thrower throws onto the start of a conveyor line it should never overflow.
Do jumping trains crash into each other?
They don't, coding wise it would be very complicated since Factorio doesn't have a real vertical axis. The train jumps as they currently are are mostly a visual illusion. It's unlikely to ever be implemented, and the ramps are hard enough to use already.
How is train pathing with the ramps?
Trains still follow Factorio's innate pathfinding, meaning an automatic train will never find a path from one rail network to another if they aren't connected (eg on two different sides of a river), even if the ramp would allow for movement between them. To make a train take a ramp, you have to guide it there using a train stop placed behind the ramp and adding it to the train's schedule
Do train ramps work with LTN?
Unfortunately not, I don't know LTN well enough to try for myself but it has to do with the fact that when a train jumps it disappears from the rail network during the jump which messes up LTN and other mods that track train IDs. Getting them to work together would require changes with both my mod and LTN (more so on the LTN side I would imagine) to specifically work together like what I did with Vehicle Wagons 2, and it doesn't look like that will happen https://forums.factorio.com/viewtopic.php?f=214&t=91039&p=519355
What items work with the Primer Bounce Plate?
Grenades, capsules, land mines, rockets/nukes, artillery shells, tank shells, and follower bots should all work, modded or vanilla, so long as they have a the right kind of action associated with them. For example, fish and artillery remotes, which are both technically capsules, do not do anything on the Primer pad because they don't have an action that makes sense. Follower robots spawn not locked onto any particular player and while they will still fight biters, they just slowly wander until they expire.
How's UPS performance?
It's okay. I personally never had any issues and most people report no noticeable lag unless for some reason you're exclusively using throwers and have thousands of items flying around at any one time. I don't know a lot about optimizing code so I wasn't actively looking for ways to make everything UPS friendly. Though smarter people than me say I did a pretty good job (or at least not a horribly inefficient job) so I'll take it 😎.
Can you still be hit by trains while ziplining?
No, while ziplining or jumping with the player launcher the character is immune to collision.
What does Renai Transportation mean?
It's a pun on Renai Circulation which is a boomer weeb meme song.