Depending on the footprint, you'll need a mounting plate. Few guns and dots will direct mount and I would bet the K series would not. However, the 507C is better sized for a 15-shot carry gun. Do some research or you'll be disappointed.
The Holosun Ronin HS507COMP is not directly compatible with the P320. To mount this optic, you would need an adapter plate that converts your DPP cut slide to accept optics with the RMR footprint. Linked below is a plate that will allow you to do so. If you have a P320 with a Pro-Cut slide, an adapter plate is not required, it would be a direct fit.
https://www.opticsplanet.com/c-h-precision-weapons-sig-x-series-romeo1-pro-adapter-plate.html
No, the TP9 Elite SC will accept optics that use the RMSc footprint. The 507 Comp uses the RMR footprint and would not be compatible. Compatible optics would be the Shield RMSc, Sig Romeo Zero, Vortex Defender CCW and more.