You id early trains by the cab #. That one as NYC #8632 (on the cab), "4-4-2" (wheels front to rear, steam ID system called the "Whyte Notation" "google it" 
) Modern era trains use a part number first and foremost, but wheels, train numbers, etc. still get used sometimes too. A "starter set", and not an awful one, but fyi you can expect much more out of the slightly larger 6 driver locos and "hobby grade" loco's in general. Adding weight to the smaller locos usually adds plenty of ability though. Every bit helps and even a half of an once can be noticable 
It may need new bushings, etc. earlier; & taxed beyond design, you should watch can motor heat, etc.. If you modify there is always "that one" 
or two 
but it's too fun to stop 
Watching a smaller engine pull like it should is like watching an ant carry a grape 
I don't own anything bigger than a 4-6-4 
Nearly all trains will slow in curves as the flanges rub (except for maybe "digital" engines). More so on 0-27, more so on longer wheel bases, and especially tight are longer ones without blind wheels (flangless). Near every layout will benefit from an extra power drop. I try to add my power feeds near the curves to defeat that.
Note, minor postion, even an inch, for lock-on change can change the track "sweet spot" for loco performance. Reverse direction Clockwise to C.C., or change to lighted cars, etc., and the sweet spots move again. Wire conducts easier than track. So add a second or third lock-on, #1 to #1, #2to #2, or solder leads to two spots on the track bottom, sanded clean of plating, etc.. More wire= easier current path, it will give you the smoothest operation. Also check that pins are tight and don't "rattle" in the host track.. You can give them a needle nose crimp on the track into the pin groove from the underside at the web. Try to keep the crimp to the outside of the rail, try not to dent up where flanges rub . A few small inside edge dents isnt gonna kill it, but isn't desirable either. (center rail isn't as much of a concern, no flanges ).
Eventually, you should look close at your pins. They made hollow ones that do a poor job if they corrode, and they do, and do so from the inside out. Go to solid pins in time, they are cheap enough, especially on the lone center rail because it carries twice the current. Look for a seam on the pin that indicates it is hollow, and or, when you have an extra, hollow ones can usually be crushed flat by pliers. You cant crush a solid pin by hand, if they crush, I pull them and put in a solid one. The hollow pins are thin enough that if corroded, the center pin may glow red hot under normal operation.
There are "3 rail gauging block", or you can make one by grooving metal or hardwood. Kinda overkill imo, but if you like a tool, you like a tool.
Also look at the tabs that hold the track on the ties/sleepers. Has the rail shifted? Is the tab set tight? (ties are a pain, rebending those super nicely is almost an art. Tinman sells a set of pliers that do both tabs while supporting the tie bottom.)
Mind the center rail insulators. Look to see those tabs are down and you aren't bottoming out a roller/shoe and riding up a raised center rail. (which already sits a fraction of an inch higher because it sits on the cardboard insulation... I repair bad insulators with cut up shoe and cereal box flaps. Some stick a strip of elctrical tape on the new insulator too.
There are pliers made just for tube track. Check with the venders in the ads. I rippers made some. I also made a rail bender out of screws, washers, Stanley bracket hardware and a block of wood, dissassembling track and bending it down to 0-17" for a few micro layouts. Nothing is like brand new, so I'll agree with "never the same", but not really so much with buying new track at every hickup.
The " nippers" referred to are called "side or top cutters". I use modified top cutters. If the handle side jaw area doesn't have a stop, you can grind the cutting edges flat and get at just the rail web (skinny upright part). Mind you a stop means the jaws won't close if you grind on the cutting edges
I've seen some "linesman pliers" that were ideal.
O gauge track has bigger pins, slightly taller, fatter ties, 0-31+ (less curve, less slowing). And it is (was?) made of thicker metal than 0-27 so is stronger; strong enough for most folk to stand on. You can reshape track ends and shim 0-27 a bit at the trasitions to combine the two.
Menard's (online) makes a low cost 31"dia. and bigger tubular O track, while you are looking around. I bought a little, I like mine
If you buy any straights for expansion, go for the long 30-40", smooth as silk and they have less connections for power to have to cross. Cheaper per inch. Cut with dollar store hack saw if needed and throw the scrap in the box or use the rail as a flat/gondola junk load.
