Difference between はもとより and はもちろん and their respective usage


I would like to know if there is some difference between はもとより and はもちろん in
the sense of "let alone" , "not only ... but also".

On a side note, I would like also to know their respective usage
(oral/written, normal/formal, modern/archaïc)

> 今の子供たちは学校 **はもとより** 塾へも通わせられている。 Children nowadays are not only forced to go
> to school but also scram school.
>
> わたしが生まれた村は、電車は **もとより** 、バスも通っていない。 There are no buses in the village where
> I was born, let alone trains.
>
> わたしの学校は服装に厳しい。制服の着方 **はもちろん** 、ヘアスタイルやスカートの長さに至るまで注意される。 My school is very
> strict about clothes. They even warn us about our hairstyle and the length
> of our skirts, let alone how we wear our uniforms.




Unless you want a very strict analysis on the differences of the two, it seems
to me that both mean almost the same thing when used to mean "let alone". もちろん
is used more often in speech while もとより sounds more formal/stiff and can also
be used in written texts/書き言葉.

A simple google search of the difference seems to agree that the two are
pretty much the same when used in this context:

[hinative post](https://hinative.com/ja/questions/11821448)  
[chiebukuro
post](https://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q13228387963)  
[Nihongo
Sensei](https://nihongonosensei.net/?p=13018#:%7E:text=%E3%80%8C%EF%BD%9E%E3%81%AF%E3%82%82%E3%81%A1%E3%82%8D%E3%82%93%E3%80%8D%E3%81%AF%E5%8F%A3%E8%AA%9E,%E3%81%A8%E3%81%97%E3%81%A6%E3%82%82%E7%94%A8%E3%81%84%E3%82%89%E3%82%8C%E3%81%BE%E3%81%99%E3%80%82)  




Unless you want a very strict analysis on the differences of the two, it seems
to me that both mean almost the same thing when used to mean "let alone". もちろん
is used more often in speech while もとより sounds more formal/stiff and can also
be used in written texts/書き言葉.

A simple google search of the difference seems to agree that the two are
pretty much the same when used in this context:

[hinative post](https://hinative.com/ja/questions/11821448)  
[chiebukuro
post](https://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q13228387963)  
[Nihongo
Sensei](https://nihongonosensei.net/?p=13018#:%7E:text=%E3%80%8C%EF%BD%9E%E3%81%AF%E3%82%82%E3%81%A1%E3%82%8D%E3%82%93%E3%80%8D%E3%81%AF%E5%8F%A3%E8%AA%9E,%E3%81%A8%E3%81%97%E3%81%A6%E3%82%82%E7%94%A8%E3%81%84%E3%82%89%E3%82%8C%E3%81%BE%E3%81%99%E3%80%82)  

