With pro analog tape recordings (e.g. 2-inch 24 track, half-inch 2-track), you record alignment tones onto the tapes to capture the state of the recording device, and then later calibrate the playback device to the particular tape so that playback alignment matches recording alignment. But this is essentially never done with cassettes, so you have to earball it.
Cassette players for mastering studios actually have alignment options (e.g. adjustable azimuth) that aren't present on consumer devices. But without the tones, you have to guess.
The problem with starting from a digitized source is that it may have been digitized from non-aligned playback. Ideally you want to go back to the analog originals - but old cassettes are rarely in perfect condition.