Interestingly, the only manuals that show the higher velocities I can find are the new Speer and Sierra manuals, and to a lesser extent the updated Nosler data. By "higher velocities" I'm referring to ~2900 fps for 225 bullets and ~2700 fps for 250 grain pills. All the others I own (Hodgdon, Alliant, Swift, Hornady, Barnes) seem to agree on ~2600/2700 fps for the 225s and ~2500 for the 250s. While the Speer and Sierra manuals list several Alliant powders with higher velocities in the 35W (Power Pro 2000, Power Pro Varmint, and AR-Comp), the last Alliant data I have doesn't list loads with any of those powders. Same with CFE223 in Speer and Sierra but not in Hodgdon.
I'll openly admit that I have no experience reloading for the 35 Whelen. My 35W is a modern Nosler M48 Liberty that really likes factory Federal 225 TBBCs, and I have a bunch of 'em. I am a fan of the cartridge and have taken whitetails, hartebeest, nyala, and eland with my Nosler M48.