In the Render Targets solution, you need to generate all objects in the main scene at the same time, and their lights may affect each other. I have developed a plugin that makes working more easier，In this solution, each UMG view component contains an FPreviewScene object, and they each have an independent UWorld objects,they will not affect each other or the main scene.
https://www.unrealengine.com/marketplace/zh-CN/product/b93b1c54b46a49d1bad5550d831a3a60