If you don't need exactly 20dB gain, just at least 20dB you can use single stage OTA. Anyhow I am not sure you can maintain with single stage exact 20dB gain for example with capacitive feedback network.
If you need an OPAmp with single-ended output, the classic two-stage amplifier should be good for you. It can handle relatively low resistive loads too, so if you want exactly 20dB gain you can maintain it with higher feedback resistors.
There are lots of tutorials about the design on the web, like this: **broken link removed** (page 26).
If you want full differential OPAmp (input and output is differential too), it is more complicated, then you need common-mode feedback circuit too.
And if the load is 100pF a very important specification is the slew rate.
https://www.radio-electronics.com/info/circuits/opamp_basics/operational-amplifier-slew-rate.php
If your output signal's peak is 1V for example, the maximum frequency is 1MHz, the SR will be 6.284V/us. So you have to know the maximum output signal amplitude to determine the currents for example.
LTSpice is good program with simple GUI and very useful features, NI Multisim has better GUI, but setting operating points are complicated, TINA is simple with nice things too but you can't set too much things in it. I suggest LTSpice.