How long does it take for E-VOA approval and what documents are needed for entry to Thailand?

Please check the eVOA application site. Most of your questions are answered there already.

1) carry photograph 1 copy, even though we upload one online ??

-> No need to have one for entering Thailand on E-VOA. But as you are travelling to a foreign country, there would be no downside to bringing an extra passport-size photo in case.

2) visa copy (should it be printed or can we show soft copy? )

-> Once your E-VOA is approved, you need to have it on the paper, printed out.

3) Is there any specific currency amount that we need to have in hand while entry to phuket ?

-> As you would pay the E-VOA fee in advance, you don't need any money to enter Thailand. But you must bring 10,000 baht or equivalent in cash as a solo traveller to enter on a VOA along with full-paid proof of accommodation and onward flight ticket.