Difference

First,it depends on the context.
Modal perfect and modal perfect progressive is like the difference between present perfect and present perfect continuous.
Modal perfect talks about actions that you did or didn't do in the past.
Compare :
She could have eaten your part of pizza.( It's possible for her to have eaten your part of pizza).

She could have be

I should have been saving ~

It would have been advisable for me to have started saving some time ago and to have continued to save until now.

I should have saved ~

It would have been advisable for me to have saved during some period of time before now.
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I could have been living ... ~

It would have been possibl

Thank you both.

@Calif,
I see, thanks. So simple form is really finished and continuous is actually going on.
But with 'I could have been living in luxury now if I had only bought that stock when it was only $20 a share.'
You said that it's possible to be living like this at the moment, but why don't we use 'could be living in luxury now if .....' then?

Thanks
lo

louiSTwhy don't we use 'could be living in luxury now if .....'

You can use that one too.

could be living in luxury now focuses on the present moment exclusively, almost as if the luxurious living were about to begin.
could have been living in luxury now brings in the past, suggesting that this luxurious living would have started som