hi bro, you have consider whether you want to save money to just have one pump. If the answer is yes, then you have to understand if one fails, all fail. Anyway, in my opinion, it will be good to have 2 returns. Incase one down, there is another pump to ensure water circulation. If you want to do T-off, you must ensure valve is catered for each opening ...this is to allow you to do maintenance. Just remember T-off will cause headloss and any elbow joint will also add to it.