Best approach to step down 220VAC to 160VAC?
1) Indeed a suitable transformer to make the 160 VAC will be hard to find. And because almost no one needs 160 VAC it will be expensive. If you were not a newbee in EE I could suggest a 120 V to 40 V transformer and then connecting the secondary in series with AC mains but that needs you to be aware of the dangers of doing this so I didn't suggest this.

2) Yes using a resistor divider to make 160 V AC from 240 V AC can be done, resistors don't know the difference between AC and DC. But again that is not power efficient and partly defeats the use of power efficient LED lights.

The actual circuit in the LED lamps also matters, some circuits simply output the same light level whatever the input voltage (within practical limits obviously).

3a) Try if the lights just work on 120 VAC, you could be lucky.

3b) Buy lights that are suitable for 120 VAC, in the end that could end up cheaper than a custom transformer.