Book South India Tour Packages – Best Destinations to Include?

Hi everyone,
I’m planning a trip to South India and exploring different South India tour packages, especially those that include the famous Kerala backwaters. I’m really interested in a mix of nature, culture, and relaxing experiences.
From what I’ve seen, most itineraries include places like Munnar, Alleppey (for backwaters), Thekkady, Cochin, and sometimes Madurai. I like the idea of combining hill stations, wildlife, and a houseboat stay in one trip.
I wanted to ask:
Which destinations are a must-visit in South India?
Is it better to focus only on Kerala or include Tamil Nadu as well?
How many days are ideal for a comfortable trip?
If anyone has done a South India tour with Kerala backwaters, I’d love to hear your recommendations or experiences before I finalize my plan.
You can check some good itineraries here: https://www.travelogyindia.com/south-india/