Simple question about the User module

I have a question as a beginner Drupal user:
I have Drupal 8 installed, the Bootstrap theme (I created a subtheme and even made a couple of regions).

On the homepage, there is no "Login / Register" link, but if logged in, there is only "My Account," and there is no "Logout" button. Also, when I go to /user/login, a block with tabs appears, as I understand it, and there we have "Login," "Register," "Reset your password." I started digging and realized that the "My Account" link is in the User Account menu, and I cannot edit it because it is provided by the User module. All I can do is rename the phrase "My Account" in the language settings to something else. But things like menu item attributes (I have a module installed that allows assigning classes, IDs, etc. to menu items) I cannot assign to this link. And the question arises why it is all implemented so complicated and confusing. I thought about it and created a couple of menu items in the User Account menu:

Login - /user/login

Register - /user/register/

My Account - from the USER module

But when I try to edit Login or Register, a message pops up saying I do not have enough permissions... It seems like simple things BUT I FOUND NOTHING about this anywhere. Here is how I see the situation and its solution: Disable all modules like UserAccountMenu Tabs and manually create a couple of custom blocks with HTML, assigning "Login" and "Register" to non-logged-in users only, and have the "My Account" module block editable only for logged-in users.
Am I thinking in the right direction? If anyone knows, could you please explain this registration and login system to me? Maybe there is another implementation. For example, why does the User module provide the menu item "My Account" but does not provide others like "Login," "Register"?