T+1 starts the end of May. Does that mean in a cash account you can do 1 buy/sell each day?

CASH accounts require waiting for settlement. After hours is still that day.

 

That is only true of some brokers. You may have the limitation but others don't. I can buy and sell multiple times throughout the day in a cash account

 

Yea, I day traded in my TD cash account years ago. But it looks like Schwab requires
trades to be opened with settled cash.