How do AAA games do blood? Games like Ghost of Tsushima, do you think it's a flipbook or 3D?

How a game will approach blood will depend on a lot of aspects, like performance, camera angle, style, focus, etc. Whilst I can’t say for certain, Ghost of Tsushima appears to be using flipbooks. There’s an interesting talk from Matt Battaglia going over how Netherrealm approached blood in MK11 which might be helpful to you! Best of luck!