Hey
Welcome to India!
Here’s our recommendation for the best back roads on this stretch.
Land in Mumbai and catch the ferry from Mumbai to Alibag. Start your cycling from Alibag, rather than from Mumbai itself.
From Alibag, you ride along the coastal road all the way to Goa. This route has multiple ferry crossings and has minimal traffic.
After Goa, enter the Western Ghats in Karnataka and ride along the Western Ghats all the way to Ooty, which is the highest point of this entire region.
After Ooty, you can cut back into Kerala and ride till Kochi along the coast or the Ghats, as per your preference at that point of time.
This way, you will get to enjoy the coast and the Ghats, try out different foods, cultures, and see a mad variety of things.
For the Mumbai to Goa leg, have a look at this travelogue. It is in the opposite direction as you intend, but it will still help you a lot. It contains all the Strava routes and elevation profiles: https://cyclingmonks.com/topic/cycling-from-goa-to-kanpur-via-mumbai/
For the Goa to Ooty leg, have a look at this travelogue. It again contains all the Strava routes and elevation profiles, which you can download:
Part 1: https://cyclingmonks.com/cycling-goa-to-ooty/
Part 2: https://cyclingmonks.com/cycling-through-western-ghats/
Part 3: https://cyclingmonks.com/cycling-nilgiris/
Alternately, if you prefer riding from Bombay to Kochi along the coast. Have a look at this travelogue, it contains the entire route: https://cyclingmonks.com/cycling-mumbai-kanyakumari/
For ‘must see’ places, I would recommend Googling along this route. There are a number of beaches, forts, temples, churches etc. which are considered ‘must see’ by tourists.
For your second question. There are many bicycle stores in Mumbai who can help you pack your bikes for the return journey. It depends where are you planning to stay in the city. But if you plan to fly back from Kochi to Mumbai, then you would need to get your bikes packed in Kochi itself. That also is possible.
I would recommend riding down all the way to Kanyakumari (south of Kochi), which is the southernmost part of India. You can Google a bit about the place and why it is significant geographically 🙂
And if you are riding through Goa, do let us know. We are based here, and would be happy to catch up with you guys for a coffee 🙂