Manuka is the quintessential smoking wood here in New Zealand. The manuka flavor definitely makes it through distillation into the final spirit.
Keep in mind this is a wood-smoked product (as opposed to peat) so the smoke flavor is going to be different. It's tricky to explain, but it acts in a similar way as smoking meat or fish with manuka. A more robust-bodied smoke that has more sweetness than peat.
You could push this all the way up to 100% manuka malt. But it will be very heavily smoked. This could be used to blend with non smoked spirits to dial in your smoke preference.
If you are aiming for a similar PPM to a smokey scotch we would suggest around 60-70% manuka smoked malt.
For a mildly smoked spirit perhaps 25-35%.