Honestly bro I'd just rock some all over stubble and keep the neckline clean like you have now. The stubble higher on your cheeks combined with letting it grow out in your mustache area will look much better. Additionally, it couldn't hurt to try the minoxidil beard that 8020beef mentioned. Additionally, I've deployed hair fibers from brands like Toppik to apply into the patchier areas for special occasions. Worth looking into.
My facial hair grew similar to yours throughout my 20s and didn't really become something I could work with until about 28. Aside from gains that minoxidil can bring, the stubble look is one that is easier to maintain and less of a risk especially if it grows in particularly patchy