Dopram V is a definate, you may not need it but is a potential lifesaver. It is used ONLY to stimulate breathing upon delivery. I have only used it once, and should only be used when you have tried every other option to get puppy breathing first. It stimulated a puppy to breathe after a point where I would have, previously, abandoned the fight for life. It is now a permanent item in my whelping kit, but luckily is hardly ever needed.
Nutri drops and Puppystim are similar: I have both but use them at different times. If a newborn is struggling soon after birth (within the first couple of weeks) I use nutri drops as this is easy to administer and you can see a change very quickly; I find it excellent when you have a puppy struggling to initially suckle or after a pup has struggled to "get started". Nutri Drops are also great for the mommy in labour, especially if it is long and drawn out as it can also give her a boost of energy.
Puppy stim is thicker and harder to adminster through a syringe style dispensor. I always keep this handy if a puppy becomes unwell when 2-8 weeks of age. It gives them a boost of nutrients when they are at their most vunerable and need all the help they can get to fight any illness.
If I had to chose only one it would be the Nutri Drops as I just find it easier to adminster from birth and the benefit can be seen very quickly.A small bottle goes a long way and both pups and mom can equally gain use.But, I always carry both just incase.
Have never used Liquid Life Aid so cannot comment on it.