This was my understanding of BF4 (at least) is that it uses projectiles and not instant hit. If you google “Battlefield projectiles vs instant hit”, that will confirm that they are indeed projectiles and not instant hit (the first two I think were not true projectiles). Instant hit has no velocity ever, because there is no projectile (correct me if I am wrong, but just going by gun mechanics & physics in real life, and experience from UE4)
Lifespan is key, along with the way you script your blueprints/C++ from my understanding (I’m pretty green to UE4 still though, so a vet might have a different perspective).
PS: I’ve actually been messing around with spawning in TONS of cpu heavy projectiles on a decently intensive map (400 at one time across the map all within visible rendering distance), and have yet to even see a frame drop directly from the projectiles (even ones with several different triggered particle effects). I see more of a frame rate drop from the foliage on my map than the projectiles mass spawning in. But that is very limited testing obviously without players connected (just developing).
My personal suggestion is go for what you think would be best suited for your game in terms of mechanics.