Well, I don't think the .35 Whelen kicks all that much. I have three rifles chambered to the round. I dunno about the NEF, but if it doesn't come with one, and I'm being brand specific here, change whatever pad they have on the gun with either a Pachmeyr Decelerator or a Limbsaver pad. Take my word on that, they do reduce the pain.
I shoot 250 gr. bullets almost exclusively in mine as that was what the cartridge was designed to shoot. It was designed to shoot 250, 275 and 300 gr. bullets way back when, because most people could not afford a rifle chambered to the .375 H&H. The long action Mauser's action alone was $100, pretty pricey back in 1922. The fact that a .35 Whelen will shoot 200 and 225 gr. bullets well is just icing on the cake.
FWIW, I am in the planning stage to have two more Whelens built. One will be on a Ruger #1B and the other on a Husqvarna FN style action I picked up a while ago. Both will have a 1 in 12" twist rate in the barrel. My Remington 700 Classic and Ruger 77 have 1 in 16" twists which are wrong for the cartridge and my custom Mauser that I picked up at an estate sale has a 1 in 14" twist, better but no cigar. The 1 in 16" twist seems to work OK with 250 gr. bullets, but if I ever wanted to shoot something heavier, I doubt they'd stabilize. I just happen to have a few 275 gr. Hornady round nose bullets made sometime in the deep dark past. The first Hornady manual has data for the bullets, but also states that the bullets were discontinued and the data was there for the benefit of those that might still have some. The manual is dated 1967 so I figure the bullets were dropped about 1965/66.
I did once see an NEF rifle in .280 Rem. it had a really heavy barrel, so there is probably a good chance the one in .35 Whelen won't be the featherweight some think it might be.
As far as recoil goes, if you handload, start on the light side and increase the level as you acclimatize yourself to the kick. The .35 Whelen is a darn good round that is sadly under appreciated by most of the shooting public.
Paul B.