How tight do you want to go Ryan
. For the loco chassis and still being able to couple wagons to it, I would recommend a minimum radius of 6inches/150mm, tighter than this and the gears start to bind and any couplings would be right at their limit. The Bachmann Brill Trolley mechanism I find is very good and copes with quite long periods of continuous running without any problems.
As a test, I got one of my Mordreds out of the stock box and tried it on a small pizza track. The base is a foot square (30 x 30cm) and the radius of the track 5 inches (125mm). It ran perfectly after first running a graphite pencil over the track and this is the first time it has been run in a couple of years at least. The closer view will hopefully show that the couplings are straining, but having said that, it is running in both directions without any trouble and no derailments, even when pushing the wagons.
Hopefully somebody else will be able to give more feedback, obviously my view of the kit is going to be a little biased