Stevie-L,
The whole matter seems quite complicated
The empirical method of trying many different brand of pellets is the simplest and easiest to do.
The JSB pellets have a low 'release-pressure', which can mean that they will be the most efficient in a 'springer', though not necessarily so.
In some of my 'springers', RWS Superdome's & H&N FTTs show about 1 ft.lb less energy than the JSB 'trio', which tend to show around the same energy (RS 7.33, Express 7.87, & Exact 8.46 gr.)
However, as far as accurate predictions go, that seems impossible.
For me, with a new-to-me rifle, I would try first, in order, JSB Express, JSB Exact, JSB, RS, H&N FTT, Boxed Crosman Premier, & RWS Superdome.
Have fun & a good Sunday
Best regards
Russ