Lonewanderer, perhaps you are right but are those cases within three hours distance wise, same make of car (but diff model), seemingly disguised, female targets, and during weird hours?
They have some things in common, sure.
Texas, early morning, CCTV footage, discussions of social media posts advertising where they would be alone at that time.
Liz's killer drove to her house, was reckless with being seen that way, shot her in her driveway point blank with no regard for who may have been around. I don't think Liz's killer is in costume. I think she is dressed like someone Liz's age who would be doing a pre-ready routine like walking the dog.
Missy's killer carefully hid their transportation from cameras and lurked in a church alone, with a ridiculous SWAT getup. This person waddled around slowly and showed no signs of urgency. Liz's killer got up to her quickly and sprinted away the second (I believe its a "she") was done shooting her. Missy's killer had all kinds of tools on them, and Liz's killer simply confronted Liz with something and shot her.
While there is some core similarities, I don't think they are much too similar after the surface level details are discussed.
If you are looking for something closer to Missy's case, check out Sheila Warren who dressed as a clown to kill her love interest, or Lisa Nowak, who had a ridiculous amount of things like pepper spray, wigs, trench coats, gloves, and drove cross country to stalk her love rival in disguise, in an airport.
If you want closer comparisons to Liz, read up on Mo Wilson and Kaitlyn Armstrong. Armstrong followed Mo on a biking app, shot her point blank at her home and put fatal shots in her while she was on the ground, like Liz. She then circled around and was caught on Ring camera multiple times. All this was in Texas, too.