Honestly I think the OP will be fine with an inexpensive rear hub. Even Crazy Lenny says most of his walk in customers prefer rear hub after riding them. I wouldn't spend too much. Maybe consider the entry level Ride1Up for $1099. It will get you started without breaking the bank.
You may want to step up to a Rad if you want fat tires for the beach. I suppose you could also look at M2S if you want hydraulic brakes, but still no torque sensing.
Surface 604? Nice bikes, you get torque sensing, good components, but you'll probably want to go with larger battery and now you're more than twice the price of the entry level Ride1Up. Similarly with Juiced. You get torque sensing, 52V batteries, good components, but how much do you really want to spend on a rear hub?
As far as worrying about flats, just invest $80 in tannus armour. Problem solved .
Tannus Armour protects your tube against 90% of common bike flats using 15mm of multi-cell foam. Say goodbye to pinch and puncture flats.
tannusamerica.com