You can only get one or the other; a single dot reticle or a circle-dot reticle. The Gideon Omega does not allow you to switch from one to another, as other makers do.
Yes, the Gideon Optics Omega Red Dot Reflex Sight uses the Trijicon RMR footprint and will be compatible with a PSA Dagger that uses an RMR cut slide.
The Gideon Optics Omega Red Dot Reflex Sight uses the Trijicon RMR footprint and would not be compatible with the P365XL. The P365 series of pistols are designed to accept optics with the RMSc footprint, such as the Gideon Optics Judge Red Dot Sight, which can be found linked below:
https://www.opticsplanet.com/gideon-optics-judge-red-dot-reflex-sights.html
The Gideon Optics Omega Red Dot Reflex Sight utilizes the Trijicon RMR footprint and would require the RMR adapter plate that can be requested/purchased directly from Walther.
The Gideon Optics Omega Red Dot Reflex Sight will be compatible with your Glock 20 MOS using the #2 adapter plate (Trijicon RMR) included with your Glock.
If you have a Glock 17 MOS (optic Ready), you will use adapter plate #2 (Trijicon RMR) included with your Glock. If you do not have an MOS model Glock 17, you will need to purchase and install the Evolution Gun Works Trijicon RMR Sight Mount which can be found by using the link below:
https://www.opticsplanet.com/evolution-gun-works-trijicon-rmr-sight-mount-1-780-in-aluminum.html?_iv_gun-model=glock-17
The Gideon Optics Omega Red Dot Reflex Sight uses the Trijicon RMR footprint and is not compatible with the P365. Optic ready P365 model pistols accept optics with the RMSc or K footprint including the Shield RMSc, Sig Romeo Zero, Vortex Defender, Holosun 407K/507K, Holosun EPS Carry and more.
The Gideon Optics Omega Red Dot Reflex Sights have a 3MOA center dot.