Nothing above DMG 3. 2 DMG and 2-20def. Maybe crit/dumb enemy as well. The whole mod is generally safe except unlimited ammo. Still, try not to use mods in visible areas like campaign or tower to avoid reports.
An alt got banned from either using DMG 7 in the past or very bad luck from checks. But main tester is still fine, alt probably banned because it is a traded account.