Hi Captain,
Welcome to the claN.
Your choice of track is good, code 55 or 80, and insulfrog or electrofrog? You mention going NCE so electrofrog would be the best option IMO.
Don't only limit yourself to Kato locos. Athearn, Atlas, Bachmann (Spectrum), Fox Valley, Intermountain and Broadway Limited are all brands that run as well as Kato models, and in most cases have detail that surpasses Kato models.
As regards rolling stock, Microtrains, Athearn, BLMA, Fox Valley and ESM have IMO the best detailed freight car range, with Atlas and Intermountain trailing.
I suggest you choose a prototype railroad, and set it in an era in time and location. This reduces the hobby spend to a manageable level and avoids ending up with an eclectic mix of equipment.
Enjoy the hobby,
Steve