Make sure that the Audio settings for the device in setup have Microphone and Speaker turned on as well as Motion Detection or the Alarm options won’t show in the Security setup.
The security settings have requirements that must be turned on before you can select them. If the Speaker isn’t on, the alarm setting can’t work, so you can’t see a setting for it. Same with Motion detection. If it isn’t enabled then you don’t have settings to control what happens when motion is detected.
I don’t think the Eufy app is unfinished, it’s just that you need to understand how the devices interact with the app. There are settings that are specific to each device and there are some that are meant to be used to control multiple devices. If the device settings aren’t correct, you won’t see the options to control them in Modes.
If I were writing the code, I would at least show the all the options and make the unavailable ones grey-ed out. That’s better than hiding them completely and confusing the users. Having said that, it’s easy to critique someone else’s work without knowing all the design details and constraints they have to operate under. I do know that their app is getting very close to the upper size limit for an Android app and that may determine why they set things up the way they have.