does 2nd Market bitcoin trust fund simply buys bitcoins as soon as they receive funds or do they pick and choose/ trade?
The Bitcoin Investment Trust (BIT) is a private, open-ended trust that is invested exclusively in bitcoin and derives its value solely from the price of bitcoin.
That means that they may delay their Bitcoin purchases for a little while after receiving cash, and they may hold enough cash to satisfy withdrawals. But they shouldn't be actively trading Bitcoin, because then the price of the fund wouldn't follow the price of Bitcoin.