Hi. I am trying to figure out what are the available alternate SPI pins for this two devices, using the Teensy 4.1.

ILI9341 Display

I am using the ILI9341_t3n lib, but I think my doubt apply equally when using the ILI9341_t3 or the ILI9341_t3n (at least when using the default SPI bus).
This chart (https://www.pjrc.com/store/display_ili9341_touch.html) shows the connections:

ILI9341 Pin Teensy 3.x and 4.x Standard Teensy 3.x Audio Board Notes
CS 10 21 Alternate Pins: 9, 15, 20, 21
D/C 9 20 Alternate Pins: 10, 15, 20, 21

I see that the alternate pins refer only to the alternate CS0 pins for Teensy 3.x, so I guess in the case of the Teensy 4.1 the alternate pins for CS would be 36 and 37, right?
What I am not sure about is the D/C pin. Pin 9 is showed as the default, which is a CS0 pin in the T3.x, but not in T4.x. And the alternate pins are again CS0 pins in the T3.x. So what does it mean? In T3.x is needed to use a CS0 pin, but in T4.x not? What pins are valid in T4.x for D/C then?

SPI Flash chip

I am using the SerialFlash library and I see the CS default is pin 6. Not being it marked as a CS0 pin for both the T3.x or T4.x, does it mean any digital pin can be used instead?
On the other hand, is it possible to use a different SPI bus with this library? or it would need some tweaks?

Thank you in advance.