I can say emphatically that energy does not kill animals…the energy transfer happens so quickly it is practically inconceivable. This is why objects hit with bullets do no fall over.
A bullets job is to expand, disrupt tissue and cause massive blood loss, bullets that fragment do different trauma than bullets that expand and stay together. So, what IS important is bullet construction that matches the IMPACT velocity, energy is neither here nor there, honestly.
When Nosler introduced the ABLR, I just had to try them out at ranges beyond their 1300fps lower limit, 6.5 and 30 cal heavies did not expand as low as the lighter bullets, yet they were still below the 1300fps velocity…so pick your bullets for what ranges you intend hunting and don't worry about energy too much…bullets going slower still kill, but aren't always reliable due to construction.
Cheers.