Buying will be cash-based and selling will be delivery-based.
Suppose stock X is in T2T. If you buy 50, you must pay for the 50. These 50 will be credited to you following standard T+2 settlement procedure.
You can't then sell the same 50 the same day and expect to get your money back the same day. It will not be allowed.
If you do have 50 in your demat you can sell the same day but your demat will be debited as is the case for a standard delivery-based sale.
Needless to say, the brokerage charges will be for delivery.
A stock is placed in T2T if the exchange suspects hanky panky such as circular trades or unusual price movements or abnormal volumes.
Some stocks such as Kernex spend a lot of time in the T2T jail. One of my favourites, Tata Metaliks, is going there tomorrow ...