New Smartthings user question about Outlets and very basic question

As @sidjohn1 mentioned, devices which connect directly to the smartthings hub, which normally mean zigbee or Z wave, do not need another app.

Samsung brand WiFi devices like the new camera and lightbulb and Samsung smart appliances do not need another app.

Other devices with official integrations will typically connect at the cloud level, and you will have to use that Device’s app to set up the device in the first place. But once you complete the initial installation, you will be able to create all your schedules and automations through the smartthings app. This would include your Lutron and Meross devices That are part of the official integrations.

The following community FAQ might also help:

[NEEDS UPDATING] SmartThings Beginner’s Guide (2020)