I voted for the Browning Safari simply because I have a Browning Safari in .375 H&H, and the stock dimensions are as near perfect for me as anything I've ever picked up. It wears a Leupold 6x42 'scope simply because it fits me so well that a lower power isn't required - I raise it to my shoulder and it's dead on - and the 4.5" of eye relief guarantees I won't get a brow cut even if I'm shooting quick from a less than perfect position.
This is an older rifle - something over 30 years old - and is no longer made, so my comments may not translate to any of Browning's current offerings. It has a Sako-type extractor, but has never hiccuped, and yes, it will even feed reliably upside down. Action is very smooth, and with some custom work (some by myself, some by a local gunsmith) it's a fine safari rifle, having accounted for lion, hippo, a couple of Cape buffalo, and various other game.
With a .30 caliber rifle, a .375 actually makes more sense to me unless elephant is your primary large game; a .375 is regarded by some as marginal for Jumbo, but it's on the right side of the margin and has accounted for a LOT of elephant. IF I were going to .458, I'd go right to .458 Lott. As a handloader, I probably wouldn't load it up to maximum, but it should be easy to equal or exceed the .458's original advertised performance in a shorter, handier package with rather low chamber pressures . . . and you always have the option of using standard .458 ammo in a pinch.
Of the rifles you list, I would not consider the Remington (I question the extraction system), the Ruger (single shot) or the Weatherby (low mag capacity, poor stock fit for me, and heavy recoil.) Plus, if your rifles arrive but your ammo doesn't you have SOME chance of finding .375 H&H or .458 Win ammo in Africa; finding .460 Weatherby would be like winning the lotto.
Two rifles, shotgun, handgun . . . better check the law, it used to be the US only allowed three guns per person when leaving the country. And that's a LOT to lug around. I think you're allowed 5 kg of ammo total, and many African countries severely restrict handguns and some types of shotgun actions.