-5 is super safe because most characters can't grab it and the only ones who can are Hayabusa, Bass, Tina and Lisa with their i4 neutral grab, which is breakable, so it's safe. Anything -8 and higher is unsafe.
The aforementioned characters and punish anything -7 and higher because they have an i6 6T, and throws take one frame to land.
Actually, @ESArion, you can't punish -5 with a neutral grab, not even offline, because as stated, throws take one frame to land.
You thought wrong! PS: Different rules apply to attacks that end in crouching status, since 2Ts are unbreakable.