Washed Up Vet - First and foremost… Thank You for your service to our country!
With regard to bullets, it’s pretty simple. Just shoot whatever premium bullet your gun groups well and you have confidence in. My son and I have shot all that stuff you mentioned plus a lot more African game including Kudu & Sable (except blesbok) with 150 grain Nosler Partitions in a .270. They’ve all died quickly. With a smaller cartridge and bullet.
It doesn’t matter whether you shoot a Partition, TTSX, A Frame, Bearclaw, Terminal Ascent, Northfork or any number of other excellent bullets. In your .300 whichever of those groups well and you’re confident in, just use it and go enjoy the experience of a lifetime.
With regard to placement, just keep it tight to the shoulder and almost halfway up and you won’t need to fire many shots. The heart is in pretty much the same place on all animals, don’t overthink it.
Just go enjoy yourself and give us a nice report when you return.