Not sure about latest AP in Model-3, but it seems to depend on speed. At 70 mr car does not change speed for speed limits (dashboard shows the limit change, I can press button to change to that speed), but it does change on TACC for 30 / 40 etc. e.g. if I come into a 40 from a 60. The reason that I am a bit vague is that I don't drive on TACC in the local A-roads / villages, so I'm not sure exactly what circumstances causes it to change - my assumption was that 70 MPH dual carriageway it ignores speed limits, whereas at/below national speed limit it changes for them. Certainly on my local "demo for mates" run car changes speed as I go into the 40, and back up again as I come out of it.
AP2 doesn't read speed limits, so will only tell you about fixed ones from its GPS database, which is sometime wrong by 100M or more
Do other cars in this price bracket have this then? (IDK)