Looking to purchase some new outlets, I've heard folks say that you can't use 15 Amp power cables in 20 Amp outlets,
If you mean the 120V, 20A outlets with the T shaped prong receptacle on one side, it is perfectly safe and legal. Here is an example:
https://amzn.to/3kLoQCW
What you may not do is put one of those 20A receptacles on a 15A circuit.
What you also have to worry about is making sure you have the right gauge IEC cable for the device you are connecting it to.
Best,
E