You absolutely can NOT rely on PIE/PIF tests (which is called PI/PO in the “scandisc” test mode) with this NEC model, which report these “errors” in a looney fashion. Actually most NEC models are not suitable for this purpose because first they don’t report accordingly to ECMA standards, an secondly they are extremely inconsistent in their reporting.
You can see that in the tests you posted: despite lots of out-of-specs PIF peaks (the red spots you see in the “PI/PO scandisc”), the reading curve is smooth and shows no trace of issues.
With this drive, you can only rely on read tests (Transfer rate test). If it’s smooth with no significant slowdowns (like it’s the case with the one you posted), your burn is OK.
As for which burning speed is better in your case, 2.4X (as others have mentioned, 1X is impossible, even if you can select it) or 4X, it’s not a clear cut. In theory, the speed giving the lowest PIE/PIF results should be choosen even when using a looney scanner, but who knows with these NEC… you can never be sure.