With respect to optics, the 2.5-8X on a M-70 .375 worked well for me in the Selous. Most of the time it was turned down to 2.5X, had that scope had a low end of 4X, my chances of successfully making a nice snap shot on a quartering away running warthog would have diminished significantly. The longest shot of the trip, about 250 yards on a wildebeest, didn't need greater magnification, but opportunities for longer shots could occur in Namibia or RSA. If you have a shot at a game animal at moderate range, under bright sunshine, but the animal is standing in the shadow of a tree of a rock, you might not be able to see him at low magnification, and this to me is what justifies a medium power variable on an African hunting rifle. My .458 wears a Nightforce 1-4X, and when things are up close and personal, the advantages of it's wide field of view can't be overstated. This is the scope that taught me the advantages of illuminated reticles; its disadvantage is that it is physically big and heavy for a low power scope, although a little extra weight on a .458 isn't much of a hindrance.
Ballistic considerations aside, the rifle you are familiar with and shoot well is the rifle to have with you. Hunting dangerous animals in challenging conditions with a rifle supplied by the PH is a bit of a crap shoot. That's how I discovered that double rifles weren't for me, despite practicing diligently with a fly weight double 12 bore loaded with slugs prior to leaving. This was a top quality British double rifle made early in the 20th Century, by John Wilkes and chambered for the .500 NE. The ammo consisted of 570 gr Xs over heavy charges of 3031 for 2150 fps, but pressure was high enough that the gun was stiff to break after firing, making reloading slow for the uninitiated.