When to use proper nouns for ideas that are given a name

A proper noun is defined as "A proper noun is a specific (i.e., not generic) name for a particular person, place, or thing" see here: https://www.grammarly.com/blog/proper-nouns/

Also here is a similar definition from Wikipedia: "A proper noun is a noun that identifies a single entity and is used to refer to that entity, such as London, Jupiter, Sarah, or Microsoft, as distinguished from a common noun, which is a noun that refers to a class of entities (city, planet, person, corporation) and may be used when referring to instances of a specific class (a city, another planet, these persons, our corporation)": https://en.wikipedia.org/wiki/Proper_noun_and_common_noun

I realize more and more despite being a native english speaker that I am never all that clear on when to capitalize something and treat it as a proper noun and when not to. Part of me thinks the Germans have it right and just capitalizing all nouns makes more sense. But I speak english, so I need a better understanding of this in english all the same.

With people and physical objects it’s usually straightforward, but I find even then it can sometimes not be so clear to me. My name is Jeff, so obviously when you refer to me by name you capitalize it because that is the name for a specific thing, me. But what if I have a room full of people all named Jeff, I could see a logical argument that the following might be correct "The jeff room was a room full of jeffs, each named Jeff", in this case "jeff room" isn’t the name of the room or a person, jeff is an adjective describing the room, likewise "jeffs" is a category of people and not the name of a specific person, so it is generic and not specific, so likewise I see why one may use lowercase. However as I understand it "jeffs" should actually be capitalized in much the same way and reason I capitalized "Germans" in my introductory paragraph. I’m not sure what is truly proper here and you could argue either direction but in this case you could potentially convince me capitalizing all three occurrences of "jeff" might be appropriate.

This seems to get even more hairy, and less clear on my part, when we talk about the names of ideas, theories, and models, anything that isn’t a tangible physical thing but rather something that is uncountable. Ideas can often have names, for example "The Three Law of Thermodynamics", which is a proper noun because it is the name for a specific idea, as can technical terms for properties for example the name for "the ability to convert current into heat" we would call "Electrical Resistance" which is again seems like a proper noun (I think) because it is the name for a specific idea, and a specific type of "resistance". However just "resistance" more generally might be lower case and could describe everything from sound resistance (walls which insulate sound) and other very general things we call resistance, it isnt the name for a specific idea, but a general idea, therefore its not a proper noun.

My issue is when does the name for a specific idea go from being a proper noun to just a noun, assuming it does at all. For example while "Electrical Resistance" is the name for a specific idea and type of resistance, rather than a general category, it would be a proper noun and capitalized. But what about when I start describing it as a general property that many different things have instead of as the name of an idea, like "The electrical resistance of this doo-dad over here is 5, and the electrical resistance of this whatchamacallit is 7, and the electrical resistance of this thing-a-ma-jig is 18." In that sense it’s no longer the name of a specific idea but rather of a general property; I am referring to a general category of different resistances across different things. So while I would expect it not to be capitalized in that sentence I just gave I might expect it to be capitalized if i used it more like this "When current is converted to heat, the name of that property is Electrical Resistance" because in this sentence it is expressed as a name of a specific non-generic idea.

So I guess my question is, Is my understanding of what proper nouns actually are correct? Am I interpreting proper nouns correct with regard to ideas, am I using capitalization correctly here? What are the rules, how can I know when to really capitalize the name for an idea and when not to?