A 16" front wheel permits the pedals to be lower, thus helping to keep the center of gravity low for better handling.
A 16" presents more rolling resistance than a larger wheel, but over 20kph the lower air drag of a 16" more than compensates for the rolling resisstance.
A 16" front wheel does not jump curbs very well.
The larger the rear wheel the smaller the big gear that is in your line of site. My homebuilts prototype #1 is 16" front and 28" rear. Prototype #2 is 16" front 26" rear.
I use regular 40psi. tires in the front. They have smooth tread, are inflated to 35psi and cost $6.99Can or $4.66US. Most of the load is on rear tire anyway.