We haven’t bought a new mixer for a decade but before that we had several installed from 1993-2012. The Australasian designed brands such as Methven and Caroma were best but pricey. Foreno says they are designed here but the cold water restriction on two of their mixers is too noisy for us but we haven’t replaced them.

We have low pressure hot water and we didn’t notice restriction of flow for hot water. We have a mixed pressure system because cold water is mains pressure. So our mixers have a restriction on the cold water flow to try to match the lower flow of hot water. The main difference we notice is the noise level.

But we are at the high-end of the low-pressure range because we use an adjustable pressure-reducing valve before the hot water cylinder. If you have low pressure from a header tank then I can imagine that might cause mixers to restrict the low-pressure flow.

Bung: Generally there's limited space in the ceramic disc valve so there will always be more restriction than a tap.

I was forgetting that ceramic valves do have a smaller opening but in practice we found the restriction of mains-pressure cold water is more limiting. We don’t notice the difference for hot water because ceramic is a half turn to fully open and washer is normally only one turn open so flow rates are similar. We would probably notice a lower flow if we had ceramic for the bath mixer.

Try looking for taps which are 'unrated' or 0-1 stars for water efficiency