A vaccine essentially simulates an infection so that our body produces antibodies against it & thus helps when we actually get infected in the future.
Sometimes and sometimes not. That's a good way to look at it for immunization purposes but not for post-exposure prophylaxis.
The point is pretty clear in the body of your question. Using your example, it takes the bacteria that causes tetanus 10 days of reproducing (making a toxin in the process) before we start to get sick. By that time, we will have started mounting a response, but if we have not been vaccinated, the bacteria that causes tetanus will have started producing the toxin in amounts greater than our ability to destroy it.
If we have been vaccinated, we have lymphocytes already geared towards making antitoxins (antibodies directed against the bacterial toxin). Giving us inactivated tetanus toxin (toxoid) stimulates the primed lymphocytes to produce antitoxin faster than the bacteria can produce it. The body's response to the vaccine outpaces the ability of C. tetani to make toxin. (If someone has never been vaccinated against tetanus, we still give the vaccine, but in multiple doses to amp up antitoxin production.)
For rabies, it's different. The vaccine itself doesn't protect us sooner than the virus would kill us. For that reason, we must also give Human Rabies Immune Globulin (HRIG) to kill whatever amount of virus we may have been infected with. So, in effect, the answer to your question
Is the number of [inactivated viruses or virus particles] delivered by a vaccine higher the number of viruses [that would need to replicate] into in an actual infection by the end of the incubation period?
is, "Yes." We don't give the live virus; that would kill us every time. But we do get pumped full of the innocuous killed virus.
Have there been trials done where they tried only immunoglobin or only vaccine to see if both are required & if yes, which has a bigger effect - the vaccine or the immunoglobin?
No. Nay, nix, absolutely not, by no means, never, no way, no how, not at all. That would be murder by the person doing that study, and a death sentence for the patient.