Need Build Advice

Starting a van build soon and looking for advice on the following components such as what brands to buy, and what not:

-Under mounted water tanks (my research is showing about 30 gallons to be the sweet spot!?!)

-water pump, I plan to have a traditional sink and a shower in my van

-Deep sink, looking for one that doesn’t take up too much counter space but is a deep sink with a flexible nozzle so that can be used for multi use

Thank you in advance