You can tell from the name Smart gaga Android 7 that it supports the Android 7 version. This is a lite and modified version of Smart gaga which is especially for low-end PCs. Well, in 7 versions of Smart Gaga, you get a high disk problem, but this problem is not due to Android 7. You can also run heavy applications like PubG Mobile Free Fire Call of Duty. The compatibility is more which means more applications.
SmartGaga 7 VS SmartGaga 4
There is no difference in terms of options between SmartGgaga 4 and SmartGaga 7, both of them run on your low-end PC, but you can run heavy applications on SmartGaga 7 because its Android version is enough.