I tested both my IDEAL 9V AC-AC transformer (US) and four SCT-013-000 current transformers for phase offsets. This is on the US side, so typical is ~120 Vac on a given standard outlet.
My single IDEAL transformer had an AC offset of 3.41 deg.
The four CTs had additional offsets of +0.54 deg, +0.67 deg, +1.01 deg, and -4.65 deg. Yes, that last one was a bit of an odd-ball.
The ADC lag between V and I can be important, but of course depends on the details. I compensate for it within my own continuous monitoring firmware with real phasor rotations. (Emontx3-continuous - New continuous monitoring firmware)
[edited 2018-12-06 to put correct AC-AC transformer phase offset]