What you are failing to understand is that the OP wants a tablet for "development", such devices should be "good enough" not top of the line or wicked fast, if you are able to run/develop your app on a "sluggish" system and works fine, it means it will be beyond crazy awesome on anything else.
Currently I use for my tests on physical devices: Huawei Mediapad M3 8 ' (Android 7), Samsung Galaxy Tab2 10' (Android 4.2), Samsung Tab Galaxy Tab3 7' (Android 4.2), Mediacom 701 7' (Android 4.10), Mediacom S2 10 ' (Android 4.2)
As smartphones use other devices with android 2.2, 4.2, 4.4, 5.1, 6.0
I do not agree that you need to use a lesser and slower product to do the tests in order to make sure it works on others as well.
Today, users have up-to-date devices and new Android versions. According to statistics, less than 10% have Android 5 or earlier. Most use Android 6, 7, and soon 8.
Having obsolete devices does not seem to have really functional tests, the new Android versions have changed the question of permissions very much. Testing on Android 4.4 or 5 with little help.
It's better to study new technologies.