Impedance matching in RF Circuit - Determine the required Q
If the antenna impedance is well matched to my characteristic
impedance, can I then simply ignore my pi network, open up the caps,
and short the inductor ?

Quite often not.
Reason: the \$\pi\$ network is also a decent &quot;remover&quot; of high order harmonics and can make the difference between a product that is able to pass certification tests and a product that will fail. The chip's output will very likely have unwanted harmonics and it will likely need to be filtered to stop cross-channel interference.
Regards estimating the \$\pi\$ filter values, you can also use this calculator. It gives you all the theory behind \$\pi\$ networks and shows how you can manipulate values to achieve a tighter bandwidth (aka cutting out those unwanted harmonics).
This is an example of a 10 MHz \$\pi\$ network that has 50 Ω input and 300 Ω output impedance and varies the transfer impedance from 10 Ω to 35 Ω: -

The top graph is probably most important in your situation: it shows that the high frequency attenuation can be as much as 7 dB at only 12 MHz. By the time you get to the 2nd harmonic (20 MHz) it can be around 20 dB to 25 dB. It's a 3rd order filter so 18 dB per octave (60 dB per decade). It will be approximately the same for a 50 Ω to 50 Ω converter.
The middle and lower graphs show the phase and magnitude of the input/output impedances.