I haven't had the chance to use the pha-979 one ( installed but wasn't tested yet )
But with the bug filter i had some issues when only trying to apply it to one set of drivers , It created a wierd delay even at 0 degrees phase shift
I think the solution is to apply the plugin to all channels and then play with the phase shift
phase bug has a built in latency delay as a buffer for phase shifting. Somewhere around 9000 so if you use it it has to be used on all channels or use voxengo latency delay on the other channels to compensate/match. The delay is calculated via sampling rate (i.e. 44.1Khz/48Khz/96Khz...) and the latency delay number of samples.
I think the voxengo phase plugin has a latency delay too but I don't remember. Console lists the latency delay in the plugins list in one of the columns.