Etwa and ungefähr

Etwa and ungefähr
I know that “ungefähr” can be used when writing e.g. approximately, circa etc. However, I can see that “etwa” can also be used for this.
Is it correct understood that both are interchangeable?
 

There is a German with Jenny about how to say approximately:
https://www.youtube.com/watch?v=FIcLpQDFWaM
There is a short promo for a French course at the beginning.
She seems to use both interchangeably although most examples are with ungefähr.

There is also this
https://german.stackexchange.com/questions/6815/etwa-vs-ungef%C3%A4hr-gibt-es-einen-unterschied
ungefähr and etwa are normally used as  adverbs however it points out that ungefähr can be used as an adjective when it is not interchangeable with etwa.

 

It is also my impression that both words are interchangeable. Lisa: Do you agree?

Another question:
Are the two words also interchangeable with "annähernd" and "rund"?


 

Hi Lisa,

Any comments to my question ?

Wish you a nice weekend and thank you for the course update :-)

Best,
​Rex