Adjective agreement with estar+de lo más

Question

When using de lo más with estar, specifically, is it preferred or more common to have the adjective agree with the subject, as distinct from when using ser for example? I noticed the specific example sentences using estar both have adjective agreement with the subjects. So I wasn't sure if this was supposed to be indicative or if it's just a quirk of having examples that were chosen at random, and I can't seem to find an answer anywhere else...

Inma Sánchez · Accepted Answer

Hola S.R
Not really, it's only a coincidence that we are using the agreement with the examples using estar. You can also use it with the singular masculine form. You won't go wrong with one option or the other. It's said that the agreement seems to be a bit more the colloquial way and the singular masculine form seems to be a bit more formal. You can read this here, but in my opinion and practice, that is very subtle and I can't really see a lot of difference to be honest. 
I hope this clarified it.
Saludos y felices fiestas
Inma