If you don't like milk powder, no worries! Substitute with 2/3 cup full fat/ UHT milk + 1/3 cup water. Somehow, tea made in low fat milk does not taste that nice - personal opinion!!!!
You can make the tea plain without any of the spices.
You can use tea bags, but it will not give you the extra strength. If you want lighter milk tea, one tea bag should be more than sufficient.
On a personal note, I prefer Eastea or Kannan Devan tea for preparation. Once you get used to the hang of drinking tea, each tea powder will have its difference. It's just like having Bru or Nescafe, though it takes time to be evident!