Is 5 + 2 hours of sleep same as 7 hours of uninterrupted sleep in your experience? What is your sleep schedule?

It's manageable but no way comparable to unbroken sleep. I practice the 4+2 hrs format during exams and I aim for 7-8 hrs otherwise.

about 6 hours with a newborn twins and a toddler

No I don't think broken sleep is quite the same as uninterrupted sleep but depending on how much broken it is, it could come close.

My sleep schedule is quite messed.

5+2 isn't even close. Most sleep cycles are more than 2 hours and you need each phase to happen uninterrupted.

7 hours sleep is better. You get more REM sleep with the 7 hour sleep

nope.

You should have at least 5 hours of uninterrupted sleep most nights (or days) but most need more. It is not good to sleep 2 or 3 hours here and there on a long term basis.