Yes, the 375 Ruger is generally sold with a shorter barrel, but the cartridge construction is different (short/fat vs long/skinny) so the powder burn is different. If you are going to shorten the barrel, you could cut off the threads, rethread the barrel, and rechamber to the 375 Ruger and get the combination of shorter barrel and full performance. Personally, I like that option better than just chopping off the barrel, but you may feel differently.
The 378 or 416 Weatherby would require you to open up the bolt face. Not a huge issue, but a consideration, as you would then be restricted to Weatherby cases if you decide to rebarrel in the future. You could rebarrel to 416 Remington and not do anything except rebarrel, that way you could get maximum performance with less powder than you would use downloading the Weatherby cartridge, or you could download and use even less powder. A customer of mine uses the 416 Remington in AK and in Africa every year, and is quite enthusiastic about it.