Scale is the most important: it is 1:29. Track gauge is 45mm., but many scales run on that gauge from 1:19 to 1:32. It is loosely Gauge 1 (1:32) is correct for that. 1:29 was considered as it is HO gauge X 3 and models were more mathematically simple to scale upwards. It was chosen by Lewis Polk of Polks Model Hobbies and became a dominant scale due to its reasonable price and fidelity to prototype. USATrains, a retailer, joined in the manufacture of 1:29 (they also make 1:24) but their product is more detailed and more expensive. Bachmann make 1:22.5 (cheap) and 1:20.3 (expensive) products. They also produce 45mm track compatible with other manufacturers. A 32mm. track is popular in Europe and the narrow gauge models than run on it. (not my cup of tea however). The rail heights do vary but the taller versions are, in my opinion, far more durable and will take more foot or paw punishment. Most purists prefer the lower heights for authenticity.
The major issue with fine scale and highly detailed models can be their exterior fragility. It is disheartening, I guess, to find bits broken off due to derailments, twigs and other obstacles fouling the ROW (right of way). Outdoor modellers are fortunate in the UK as tunnels and one or two other structures can be sited. We do not have the nasty critters found in much of the USA and Australia such as snakes, scorpions etc. that set up home in such places. Moreover, few of us have, bears, deer and so on that can wander over and damage our tracks and buildings. Our climate temperatures are also much less aggravating. Friends in Canada for instance pack all away from early October until May. They are usually knee deep in snow. Very high temperatures, found in some countries, can cause expansion issues to track - just like the big railways! Leaves can be problematic as well - again same as the big guys. But maintenance and visual checks are part of it - just like the big guys again!