Everything about new bright is smaller than G scale. They run on G scale track, but they otherwise seem like a smaller scale to me. Their wheels are smaller. If they had people they would be much smaller. Some of them have nice bells and whistles, but they are a cheap chinese toy grade in my opinion. A lot of the cheap chinese toy trains use their own style of couplers incompatible with the more serious brands. Scientific trains are probably just as cheap as new bright but are closer in size to better brands. New bright may be the smallest of the supposedly G scale trains. Eztec and Echo trains are much larger than newbright but also smaller than scientific. And scientific is a bit smaller than playmobil, LGB, Bachmann, etc. I have a bunch of new bright stuff I want to get rid of. Don't even think about running newbright together with LGB; if you do you might as well get N scale to work on HO track and run N scale with HO.
By the time you upgrade them with better wheels, and other fooling around, it might be the same cost as buying quality stuff used. They use REALLY cheap plastic that can fall apart. (steeling myself from the next post by someone that has a 100 year old New Bright that works just fine)
Not sure about New Bright, but some 20 years ago when my lad was just a little'un we had some cheap G sets appear in our local Lidl store for £25. By Scientific Trains I think. Battery powered loco/lender plus a couple of 4 wheel trucks. I remember the couplings were hook and loop style but the opposite way up to LGB, ie. with the hook above the bar (similar to Triang/Hornby OO). Very cheap and cheerful but it worked for a while. After a few years I did fit LGB hook/loops to make the trucks compatible, but they were little used as by then we had Playmobil and Toytrain items for the youngster to play with.
I don't think I have the trucks or tender any longer, though they may still be in the back of a cupboard. I know the loco is long gone.