Yet all of the above have been collectively called "G-scale" or "G-gauge" by most folks, though there are many recent efforts to separate them. Such as 1/20.3 is called 'Fn3-scale' (Meaning F scale or 1:20.3, narrow gauge, 3 foot)

Now that you think you have all that straight, I'll throw you another curve. The toymakers don't always stick to pure scales.... There is a LOT of 'selective compression' and just plain use of "rubber rulers" in large scale. The main reason was so that the new stuff being brought to market could also be used (more or less) with what folks already had (so we're back to LGB again)... A 1/29 standard gauge 40 foot car is similar in physical size to a 1/22.5 narrow gauge 30 foot car. On some items there are even multiple scales employed on the same model to make it 'fit'.  (Also consider, an accurately scaled 80 foot passenger car would be nearly 3 feet long and would have a very difficult time negotiating curves on all but the largest layouts!)  Worse yet, sometimes stuff from the same manufacturer, STILL doesn't always look good together.

AND, to put the icing on the cake ----- Many manufacturers don't even bother to state the nominal scale of their products on the packaging or in their literature, leaving the customer to guess!

Now, just for fun we'll throw another large (scale) monkey wrench into the works. Most available non-train acessories are either 1/32 or 1/24, with a few to be found in 1/25 or 1/18 as well (people figures are about the only exception)....... so scale fidelity pretty much goes right out the window all over again!

Hence the confusion.

Unfortunately, there are no hard and fast rules of what works with what, and what doesn't. A few folks are scale 'purists', often resorting to building much of what they need. Some folks choose to buy only from one manufacturer to try to keep things somewhat the same scale. Most people just run whatever looks good together, regardless of scale. And some others are quite happy to run a complete hodgepodge. That's one nice thing about large scale, as long as you like it, it is right - even if it's wrong. Large scalers humorously refer to this as "Rule-8" (It's MY railroad and I will run what I like, when I like, and how I like - and if YOU don't like it, you can always find the door....)

The best advice I can offer for those who are worried is, "If in doubt, measure." Generally a tape rule doesn't lie. Measure things like doors and doorknob heights, windows, and wall heights... In the real world this stuff falls in a pretty narrow range, --- as well as the overall dimensions. If your memory is lousy like mine, make a list of the sizes of stuff you already have BEFORE you go shopping, then keep it in your wallet. When ordering by mail or online you should ask the seller to measure it if you're not sure. If they are "too busy", then they really don't want to sell it very badly. Call another vendor - it ain't really a 'bargain' if turns out that you can't use it.

About the only really positive thing about the whole scale mess is that, whatever scale you choose, you can take a train when you go visiting another large scaler and know, other than a few possible clearance issues, you can run it.

Clear as mud? You'll come to think all this is 'normal', eventually....  As the Cheshire Cat said to Alice, "We're all mad here."