Is ISE in RVCE a better stream than ECE? Can I switch my stream to ISE in third sem with a GPA of 9.20 in RVCE?

Okay this is a bad way of looking at things. ISE and ECE are very distinct subjects and people get into one of these because they either have some exposure to the ideas of the subjects or are keen on building some interest toward it.
If you’re getting Ece, I’m pretty sure you’ll get ISE as well. Both ISE and ECE departments have good faculty, placements and everything. The choice is a personal opinion. We guys at quora can’t tell you what you want to do in future.
Sit back. Think about it. Whether you’d wanna code, or you’d wanna learn more electronics stuff.
And as far as branch change is concerned, yes it is possible. The exact numbers I don’t have, but anything north of 9.2 should keep you safe. Don’t rely on it too much.
Tell yourself you’ll be okay with studying ECE if you don’t get a branch change.
I know this a confusing period in a students life, but sometimes you’ve to make choices and look at what you’re gaining, not what others are and you’re not.