1. I know it is easy to create multiple stores, but no idea with how to create different themes for these two stores
I hope that you have configure your theme for one store. now you have to change the color combination of different store. so you have to create new theme.
Suppose
app Skin
--design --design
--Frontend --Frontend
--default --default
--store1theme --store1theme
Now you want to change only css then copy and paste the theme folder skin folder like below
app Skin
--design --design
--Frontend --Frontend
--default --default
--store1theme --store1theme
--store2theme
now go to your admin panel. System >> Configuration >> Design
Now you can see the "Current Configuration Scope" at starting of left menu. just click on that and select your store 1. Then it will redirect to the page. same as below
So this way you can set diff theme for diff store.
2. How to introduce a new landing page in Magento CE,
Its Simple create 2 cms page with same identifier and just the set diff store. Magento has functionality that it will call the pages as per store view automatically. just like below Image
Hope you got the proper Answer.
Best Answer
When new Website or store view created you have to run the following command in your commandline,
Once this done, you can able to see your new store in design section to edit and set the custom theme.