I have just ordered a NUCLEO-F446RE. It is Friday. So it might not arrive tomorrow.
Yes. Run the Arduino Boards Manager. Install the "ST Cores" from ST Microelectronics".
Most regular Arduino sketches should run out of the box. Sketches that are dependent on hardware might need to be "slowed down" for the 180MHz F_CPU.
When my F446RE has arrived, I will add support to the MCUFRIEND_kbv Beta on GitHub and verify that the examples work. Then I will probably issue the pending Release. So it is available through the Library Manager. Do not trust guy selling it on ebay
Note that ILI9320 class of controllers can not run as fast as MIPI controllers like ILI9341, ILI9486, ...
David.