Using ALTPLL and ALTCLKCTRL (Clock Muxing)

Actually, be sure to look in the device handbook. For pretty much all devices, the altclkctrl can only switch dynamically between outputs of a single PLL. There is no way to mux in the original clk. (The reason the altclkctrl has all its possible connections documented is because it is the global clock tree driver, so it's documenting how things get onto it, but most connections are static based on the bitstream.) If the two outputs of the PLL do not match the input clock's frequency, create another PLL output tap that does and use that.