2018.1 was in beta for quite a long time and I'm confident of it's stability. I installed it yesterday and I can say with all the new features, it's much better than 2017.x. I didn't download the beta so this is my first time using 2018.1 and its awesome! I said I may only support 2018.1 and higher but I think the best approach would be to support Unity versions from 2017.4 and higher. During the next beta, I will test both versions to make sure there aren't any compatibility issues. I'm currently testing out RGSK 2.0 in 2018.1 and haven't run into any issues so far. There's a high chance that v2.0 will use Cinemachine for the camera system and the new package manager in 2018.1 ensures that you can get all the latest updates.