Site-portal or placement of departments on subdomains?

Question

Search Engine Optimization

You need to create a website for a company that creates websites and other related activities.
For example, for the creation, promotion and support of sites, as well as hosting and domains, you can create a single site.
But will it be normal if you place on the same site such sections as:
Creation of spherical panoramas of the interior, system administrator services, repair of digital equipment.
Initially, there was an idea to do everything on subdomains, in general, to separate all types.
Place general information about the company on site.ru and send it to individual user services.
For example, seo.site.ru, direct.site.ru, studio.site.ru, hosting.site.ru, domains.site.ru and so on.
Additional activities should also be moved to subdomains.
panorama.site.ru, admin.site.ru, remont.site.ru.
Each subdomain can also be used for direct, in order to immediately attract targets for a specific service "without water".
Actually, how correct and good practice is this to implement?
Or a single "portal" where there will be categories site.ru/seo/ , site.ru/panorama/ and so on.
And the main question is, I want to bring all these subdomain sites to the top of search engines so as not to bother with direct.
How feasible is this at all? Or is it more correct to shove everything onto one big portal and promote it already?
But then the question is how well a huge number of services that are not strongly tied to each other will get along.
There is also an idea to implement a blog.site.ru blog, where unique articles will be written on each of the topics.
Again, it all depends on the first answers, do blog.site.ru or site.ru/blog/ .
All sites (if these are subdomains) will link to each other, for example, somewhere in the basement there will be a section common to everyone, called, for example, "Other projects of the company".
Clarification.
The sites will have the same contact details and details, perhaps only the phone numbers will be different for call tracking. Again, this is in case there are different sites, subdomains. The design and layout of each site will be unique.
More questions than answers

Answer 1

The site is primarily a benefit to visitors (90%).
And only then - collecting money from them (10%).
Therefore, it is better to do everything on one domain in the form of a blog in different directions with offers of your services (at the end of the article or somewhere in the bar: left / right, etc.)
. each of them will have a minimum "weight".
Better - all on one with categories in the URL path.
If you want a unique design for different sections, it's not a problem: you can make your own layout and design for each section.
Logic: in order for me to order something, I must understand: what and how well those whose website know.
Even if I don’t understand / don’t know the subject area, I would give a link to someone who understands and he would be able to quickly assess your knowledge and potential for developing my project based on the blog content.