The primary concern isn’t so much what faucets you use but where the features are placed. Due to the fact tankless water heaters only generate hot water when the hot faucet is open there can be a delay to heat to the required temperature.
Any faucets that are too far away from the heater can be prone to a ‘sandwich effect’ if the hot water is used intermittently. You can fix this by using a recirculation pump that runs the water from the furthest fixture back to the heater and keeps the water hot but they tend to use a lot of energy. Preheating or buffering the hot water is recommended.
Another thing to watch out for is if the faucets or shower-heads are prone to suddenly increasing the temperature when you draw cold water from somewhere else. This could result in some nasty burns. A pressure-balancing tub and shower valve will eliminate the problem. Until then try to be careful if there is someone using the shower.
One of the best tips involving your faucets is to install water-saving aerators on them. This will help to prevent hot water being wasted when you leave taps running i.e. washing vegetables, etc.
If you measure the flow rate of your kitchen you should then replace aerators on faucets that use more than 5.7 litres of water p/min. Before buying a new one, remove the existing aerator to take as a sample to make sure you get the right save. Choosing a model with a flow rate of 5.7 litres per minute is best.
The other very important point here is ensuring that your faucets give a minimum flow rate high enough to activate the heater. Single handed bathroom faucets may mean you have to open them as far as they go to get the right flow rate to get the heater to fire up.
This is even more likely to happen in the summer. Find a heater model with a minimum flow rate of .5GPM. Low flow related problems are still possible but with models of this size they are at least easier to solve. Otherwise this can be an expensive problem to fix. Also, debris in faucets can cause the flow to drop to a level that will stop the heater from firing up. Making sure the faucets don’t have any debris in them can help to avoid this.