Biology is very complicated and many people tend to over-simplify some aspects of it.

Viruses are so small that it is hard to see with normal light microscopes, but they are a major part of nature in numbers.
So here is a small overview with pre-2019 evidence. So I avoid the false-positive problems and propaganda with SARS-Cov2.
There are a lot of videos that only show drawings, and I try to avoid them.

A virus hijacks a cell to replicate and spread itself. It works a bit like a computer virus.
So it uses a lot of the existing components of a cell, and set them up to work for the virus.
The virus contains a RNA code or DNA code that needs to be activated inside a cell to work. So different viruses have different techniques to get into the cell.
Just like computer viruses use many different tricks to get into your computer system.

One virus or a million does not mean that you get ill, or that you can spread it.
The working conditions of a virus are very limited, and the various immune system parts will attack a virus. A virus is uses the easiest and weakest targets to spread itself. Targets that must be exactly matching the hijack techniques that the virus uses.
The immune system reacts almost immediately to an effective infection, giving you various symptoms. So you can not really spread a virus, if you have no symptoms. And just before getting sick, you are spreading so few viruses that the humans around you will have time to build immunity.

Hypothetically, the only asymptomatic spreaders are people that have IgG4 due to boosters. The IgG4 causes the immune system to ignore the recognized virus. There can be various immune system problems due to "vaccines' that hide symptoms until it is too late.

A virus can not sustain itself for a long time, so it needs to hijack a host like a parasite. It can not even adapt itself (except maybe the giant versions), and mutations only happen by accident during replication.

Some viruses look like exosomes, because these viruses use the same system. But they differ in that the virus code gets replicated and spread from cell to cell.

Here is the plant virus visualized in a video: https://www.youtube.com/watch?v=wOxeJ0aEptU&t=1084s

Viruses can also be very big. Giant virus infects Ameoba https://www.youtube.com/watch?v=F3476UHJAFQ

Cell Biology of Virus Infection. The Role of Cytoskeletal Dynamics Integrity in the Effectiveness of Dengue Virus Infection https://www.intechopen.com/chapters/49374 There are many such books, from which you can learn things. And you can see that they have done a lot of work in laboratories.

Here is some discussion about exosomes and viruses. https://www.cellgs.com/blog/exosomes-and-viruses.html

Extracellular vesicles and viruses: Are they close relatives? https://www.pnas.org/doi/10.1073/pnas.1605146113