foreign income, transfer it to my savings account in India
Yes you can transfer to India. The right account would be NRO/NRE. As an NRI one should not hold a regular savings account.
forum that foreign income is not taxable unless used to buy stocks, fds etc
If you are an NRI, income earned outside of India is not taxable in India. However any income you generate in India is taxable, i.e. interest income, gains from shares etc.
Do we need to pay taxes for the money transferred
No tax if you are an NRI even if you transfer funds to India. Taxation does not depend on whether or not you transfer the money, it depends on your status
used to pay home EMIs or principle amount?
You can use the money for what ever you like.