First; a 30" diameter LP cylinder will supply 289,000 Btu at full flow on a full tank. Drawing more than that WILL freeze the valve, usually open and causing most people to get long sticks and big bags of marshmallows.
30" diameter tanks include 20#, 30#, 40# and 100# tanks. With the advent of Government mandated OPD valves in tanks of 40# or less flow is restricted to 80%. Any burner drawing over 289,000 Btu should be serviced by at least a 250# 'fat-boy' or a minimum of two 30" diameter tanks. There are new 44-45# industrial tanks on the market with POL fittings and full flow.
Second, a gear box drive adds another oil resivoir that needs to be monitored. It also adds more seals to leak oil. Yet it still keeps a mechanical connection between the pump and engine/motor. Therefore if one component fails the others will too. This is a low cost, stop-gap, measure that is used to give the appearance of custom engineering. There are instances where gear reduction drives work as intended for packaging reasons but the compromises do not warrant it, IMHO.
Third, there are literally thousands of LP fueled commercial vehicles on the road every day. The DOT does have very specific rules governing the transfer of LP over the road but they are well known and fairly easy to deal with. (Just look at David Olsen's rig at Tidy Pressure Wash).
A national manufacturer with an established dealer network will always give you recourse if something goes wrong. I do applaud you getting your Card company involved to get results.
Larger manufacturers will also have the resources to build equipment for inventory or their dealers will have the wherewithall to do so. Also larger manufacturers will more often have professional packaging that may reduce transport damage and use components that either meet Gas Association standards or, better still, are inspected and approved to meet/exceed those standards.
Essentially what I am saying is you get what you pay for. Regional manufacturers with no local dealers have no responsibility to you once they have your money. Price does not mean performance in either direction.
Find a local professional pressure washer dealer to work with you and help you get what you need for your intended use, not what you think you want. The money paid up fron will often pay dividends later.