There's no exact equivalents to either Unique or 2400, in terms of either charges weights, or direct substitution.
Hodgdon Universal was designed to be similar in range of usage to Unique, but NOT the same charge weights (hence the similar name for marketing purposes). However, Universal is essentially defunct. It has not been readily available since a fire in the manufacturing plant in Australia in 2013, and a switch to production in Canada has not rectified the situation.
Hodgdon HP-38 and Winchester 231 are the exact same propellants. Winchester 296 IS NOT. The confusion perhaps lies in similar names. HP-38 and W231 are relatively fast burning powders, faster than Unique.
Hodgdon H110 and Winchester 296 are the exact same propellants. These are slow burning powders with very specific loading data. They do not function correctly with reduce charges.
Best advice is to go the Hodgdon Data Center website, look at the loading data for cartridges you use, and velocities you want to achieve, and buy those propellants. Hodgdon also owns Winchester, IMR and Accurate brands, and that data is listed as well.
Most Hodgdon-sold propellants have good availability. The old Hercules is long dead. Screw Alliant.