With: Eevee, 2.8.6, 2.9.0, macOS 10.15.4, Radeon RX 580.
My Temporal Anti-Aliasing is quite bad, it's very anoying. My TAA is good for meshes through to Film>Filter Size parameter.
If I put "1" to "Anti-aliasing Threshold" it's much better than "0", but not enough. If I try more than "1", it doesn't change anything, it doesn't blur the GP, even if I put "1000". I've tried to increase Sampling>Render, without success.
In "Hero" by Pepe Land, I can see there is no flickering due to aliasing, so it must be possible.
Here is my file, thanks!