Too often I run a program where either I have to select Run As Administrator to have administrative privileges or I can't do something because Windows says I don't have enough privileges
Well, you could refrain from running programs that ask for Administrator or other extra rights.
Most programs designed for window 7 or later that do something for a work, leisure or hobby purpose don't require Administrative rights. You should only need administrative rights for making system wide changes, such as installing a new program for all users.
I am the only one with access to my computer. After going to Settings \ Accounts \ Your Info, I can confirm that I am listed as the administrator.
What this is telling you, is not that you are 'The Administrator', but that your account is a member of the administrators group.
Every user is logged in with standard user privileges then that Admin prompt is used to grant Admin privileges for specific tasks.
That's how Windows was designed.
Technically, that's not how it works. You're logged in with whatever group memberships you have, but if you are a member of the administrators group (or other group with extra rights), then those rights are dropped before explorer starts. This feature was introduced with Windows Vista. The idea was to get developers to make programs work for non-administrative users. Your opportunities for wrecking your windows installation or interfering with other users of the same PC are reduced if you run without administrative rights. You may be the only user of your PC, but windows is designed to enable more than one person to use the PC (although not simultaneously).
I've looked in Local Group Policy Editor and Registry Editor (after saving a copy of my registry, of course). But I can't tell what I'm looking for.
You're looking for the group policies for 'User Account Control' (UAC). The default setting is fairly slack, but there are even slacker settings. My advice would be to use a non-administrative account for everyday use, and set UAC to the strictest settings. There's a tutorial on this website that tells you how to do either of these.
The Windows Vista settings for UAC were very unpopular with a vocal minority of users. "It's outrageous! My new gun has a safety catch and a trigger guard. I know what I'm doing, I don't need this." Microsoft made a big effort to fix some of their issues with Windows 7. Many to enable non-admin users to do things that Microsoft thought that it would be reasonable for them to do.
Mark Russinovich explains the changes made in Windows 7, and includes links to his series on Windows Vista and UAC in
User Account Control: Inside Windows 7 User Account Control
I think it has already been suggested to you that you should use a virtual machine with a copy of windows so that you can experiment. There are two other possibilities you might like to try.
Windows Sandbox which is a feature of Windows 11 Pro. This gives you a playground with full admin rights, so you can try random bits of software, or registry tweaks. This is very easy to do, and your changes disappear when you close it.
The other is to make a new local account without admin rights, and see if you can figure out how to do things without admin rights. If you mess up this account you can log out, and delete the profile with your admin rights and start again.
You may find it quite hard to learn about how windows is organised and works simply by experimenting, some people find books helpful. There are a lot of them, and of variable quality. If you ask here, I expect you'll get some recommendations, but do think carefully about your question. "What's a good book on Windows 11", probably isn't a good question.
Finally, if you have a specific issue about the requirement of a particular program for admin rights, then ask about that, and explain what you want the program to do for you.
For instance: "I just want to look at the registry, but every time I start regedit it produces a UAC prompt, how can I avoid that?" might get you an answer.
