You may get a dribble from the taps if you use high pressure type.;

If the shower is pumped then it's classed as high pressure.

Probably the worse taps to choose for a low pressure gravity system are quarter turn ceramic cartridge mixer taps that are designed for a single hole in the basin. To get the pipes through that hole flexible hoses are normally used and the internal bore can be very small. Have a look at examples in the DIY stores. Also take a look at the hole in a ceramic cartridge, even fully open less than half the area is available...



The best type are probably the old fashioned victorian bulbous taps that use a traditional washer. The bulbous shape was designed to allow plenty of area for the water to flow through when the washer is lifted off it's seat. They were that shape for practical reasons.

For a a low pressure gravity system choose taps that say they only need 0.1-0.2 bar (= 1-2 meters of head).  If they are modern quarter turn ceramic types check you can take them back if they don't perform as expected.

Aside: Actually it's a bit meaningless to say a tap needs 0.1 or 0.2 bar. That's like saying a light bulb needs 240 Volts when you also need to know how bright it is to compare it with other bulbs properly. Ideally the specification for a tap should say something like "This tap will deliver XYZ Liters of water per min when connected to a 0.2 bar source".