How to properly organize a multi-module portal in terms of SEO?

Question

Search Engine Optimization

Good afternoon.
Now I'm facing a dilemma, how to properly organize a multi-module site.
Detached example to understand the problem.
There is a community: "hairdressers". A portal is being created for this community.
The portal will consist of several large sections:
1. Search and information about hairdressers and hairdressers
2. Training for a hairdresser
3. Products for a hairdresser
Each section links to another.
The question is, how is it better to organize such a portal from the point of view of SEO?
1. Separate sections into subdomains, providing linkability between subdomains
2. Do it all on the same domain, providing more internal links
Questions of technological risks and resources do not interest me in this matter.

Answer 1

Considering that the topics of the modules are completely different, it is better to split them into subdomains so that it is easier for the search engine to figure out where and what.
In addition, no one is immune from changing relevant pages within the same site for only-robots-known reasons, it can be hard to restore later.
I vote for the first option