All efficiency data can be found here: https://www.notebookcheck.net/Intel-Panther-Lake-Core-Ultra-...

The most important one for efficiency is ST perf/watt. MT perf/watt is largely based on how many cores there are. You can achieve better MT perf/watt simply by having more cores (more transistors) and run them at lower clocks. Panther Lake also has an entirely new MT config with 3 tiers of cores vs 2 for Arrow Lake.

For ST perf/watt, it loses to LNL.

Keep in mind that LNL and Arrow Lake used N3B, and future N3 nodes have been much more efficient. Panther Lake CPU is also a new design which should have improved perf/watt automatically regardless of node.

Based on this, one can deduce that Intel 18A is likely a bit worse than N3B and perhaps equivalent to N4P. Keep in mind that N3B went into production in late 2022 and N4P was a 2021 node.