I think barriers are not a problem for most racers. You have to avoid them, just like a grass or high curbs on normal tracks.
One of the problem that is often mentioned by the people on the server, are FPS. Some layouts are really big and sometimes have to much spare objects in my opinion (like tyre stacks inside every corner at The Maze layout). Also the first race 9 laps lenght 'bug' is scaring people from staying on the server.
Most fun and good racing you can see at quite simple and not objects overloaded layouts. Wobblyoval is a great example - so simple and so much fun! My favourites are ParkWay* and Figuratively combos because they provide great racing, and also PitOfDespair & BusterSprint2, due to crosses and jumps
As for cars selection, I would say XRG and TBO's are the best for this kind of driving. LX4 is too tricky and light (easy to push into a barrier), so would be the LX6 propably. What about MRT5? It's a car destinated to be used on autocross...
Anyway, I would like to say "thank you" for the BnJ server, as racing on the layouts can be great, and no-one did server with that many layouts before