Even assuming the same ecological conditions, efficacy of a vaccine is in a (dose-dependent trade-off with side effects. (This was e.g. easily shown in the phase I/II trials of Moderna's vaccine.) Even for the exact same tech/vaccine, manufacturers may choose different points along this curve.
Furthermore, the amount of "training" and thus resulting levels of antibodies etc. depends on how long the injected vaccine lasts in your body. There are numerous factors that affect this, see e.g. prior discussion here what affects that in mRNA vaccines alone.
Changing the delivery vector to something more substantially different, e.g. from a lipid nanoparticle (LNP) to an adenovirus (Janssen, Astra-Zeneca, Sputnik) can have more substantial effects in both of the above regards; i.e. the side-effect vs efficacy profile may be on different curve; the technology that makes a pure mRNA vaccine persist long enough in your body is not the same as that using an adenovirus--by the way, the latter is a DNA virus, so the protein is coded in a slightly different substrate, with a different "decay rate". You can also have prior immunity to some adenoviruses (and also develop it from the vaccine, I think).
Furthermore, some other Covid-19 vaccines (e.g. Novavax) deliver the proteins themselves (in a LNP) rather then mRNA, so they are even more fundamentally different than mRNA/DNA based ones with respect to all of the above. The same mRNA molecule can get reused a good number times in a cell to produce (spike, in this case) proteins, but a protein is more or less of "one use" for the immune system. Generally speaking, protein vaccines (and this include's Novavax) use various adjuvants to get more immune response out of the same dose of proteins, which are fairly involved to manufacture. (Such adjuvants aren't used by current mRNA vaccines that have been approved, probably because they generate [translate to] more than enough proteins.)
Of the vaccines you've listed, Pfizer/Biontech and Moderna are the most similar to each other technology-wise (both mRNA in a PEGylated LNP--their actual formulation differences are somewhat obscure), so somewhat not surprisingly they produced the most similar results.
Additionally, small changes have been made to the genetic sequence of the spike protein; more specifically
- Astra-Zeneca & Sputnik don't report any modifications
- Pfizer and Moderna (both) made the same proline substitutions
- Janssen additionally made two mutations at furin cleavage sites
- Novavax made three of those
The role of proline substitutions is to keep the (produced) spike protein in the prefusion conformation for a longer time, thus effectively increasing yield. If you wonder how they both got this idea: it's because this was first
done on a MERS vaccine.
It was observed that most of the naturally produced antibodies target the
RBD, which is only exposed in the prefusion conformation.
According to Janssen's pre-clinical research, their furin mutations have an additional
stabilizing effect and cause the host to produce a greater ratio of neutralizing to non-neutralizing antibodies (compared to the variant with the two proline substitutions only). Novavax basiscally did the same thing but altered the cleavage site at three points RRAR→QQAQ.