Most free or very low cost sizing and selection software given away by a vendor is generic by nature and won't contain all the selections that their in-house propriatary sizing software will give them

You will either have some special constructed regulating composed disc, cage type or similar, to give support for a complicated and large pressure flow and drop.

For steam service, it depend on the pipe sizes, pressures and temperatures of your application.

Currently researching LNG cryogenic service valve...Metal-seat Triple-offset Butterfly Valves (TOBV) are well-suited to LNG service. They are very inexpensive for inch of diameter.

Bubble tightness is a wide terminology which simply means zero leakage when the valve is in close position.Now if the medium is water then the valve should have zero leakage at twice the rated pressur

The standard way to calculate dynamic torque is to run a flow test and measure the torque required to rotate the valve at each position.

Triple offset valves are set up much like double-offset valves, except that the profile of the outside diameter of the vane is machined as a conic section. The cone would be projected upstream,

Double-offset valves, also known as high-performance butterfly valves, have the shaft mounted slightly offset from the pipe centerline, and the shaft is mounted behind the sealing band of the seat.