Customizing my theme

It’s not a stupid question.
As you have found, WP is not a design-each-page sort of system. WP doesn’t actually do anything for the front end. It provides functions to retrieve the correct data from the database, and the theme is responsible for outputting the HTML. It would be unusual for a theme to show different things on different pages, as if the user had to build each page separately. The theme makes it simple to keep the site consistent.

The Site Identity is a core option, not a theme option. It is used by the theme to output the site title, but it also appears in the footer (usually copyright text) and in the feed and in the <title> that shows in the browser window. So trying to put an image there doesn’t make sense.
There is another core option that is a custom logo, which the theme may or may not handle for you. (most do) This is an image, and the theme dictates the dimensions that fit in with its design. Or you can put it in the header image, which is also a core option that the theme implements (or not).

Choosing a font would be done when you create the image, and isn’t part of WP or most themes or plugins. (you might find a plugin for SVG logos or something; I haven’t looked)
The theme usually chooses some fonts as part of the design, or allows choice from Google Fonts. There are plugins that do this also, independent of the theme.

There is a general editor for entering the content of each page, but it does not apply to the common areas that are on each page. (not until Full Site Editing comes out, supposedly in WP 5.6) Meanwhile, you should be able to switch themes easily to one that has some options for what you need. The built-in themes are intentionally sparse in options because they are the fallbacks for when your chosen theme breaks.

Sounds like you got the bones and structure of the site up already, congrats! Those are big steps ??

As for the design and front-end of the site, I would check out https://themeforest.net/ where you can review and shop through a lot of different themes that best fit your site.

https://www.wpbeginner.com/glossary/child-theme/ is for some background on the relationship and creation of parent and child themes and their structure required via WordPress.

Regarding “an order form (which I guess I have to write myself?)” – something also to become familiar with WordPress are ‘plugins’ and their usage. For forms specifically, Contact Form 7 is a very popular form plugin to use for your request of an ‘order form.’

Usually plugins that have a high number in downloads / installs, have recent updates, tested for most recent WordPress version, etc. are indicators that they are reliable and well supported.

I hope this helps!

Thank you, Joy and gmatzy, for your excellent responses. I found them kind of by accident, since this support forum did not send me notifications of your postings. Some fora send notifications instantly rather than batching them up, and I find this more useful for knowing what is going on.

I have ideas about creating my own website/app IDE, and I’ve actually done quite a bit of work toward that goal, but I’m months away from being able to create my own modern and professional-looking website, and Google is putting pressure on me to update my website to make it work better for advertising, so I’m not going to abandon my experiment with WP just yet.

The thing is, that what WP does best (serve many similar pages from a database) is just what I don’t have any need for, since there is only one product and just four services associated with that one product, but lots of static pages of explanation.

I need to find a way to go through the hundreds of themes that are available, so I can see what might work for me. I will check out Theme Forest, thanks.

Does anyone know of a free or low-cost product that handles design-each-page, full site editing? That sounds like a much better fit for my needs.

Also, I’m feeling doubtful that any plugin will provide the kind of detailed order form (looking more like a job application form) that has many specialized fields to ask about my clients’ relevant background details. I programmed my current order form in PHP to match my order input program, so I fully expect to have to do the same for my next website version, although I will need the style/appearance of the order form to match the rest of the website.

I just can’t wait six months until I develop my own ideas into working software. I need some way to update my website more quickly. Is WP that way?

There are page builder plugins like Elementor and Beaver Builder, but I don’t use them, so I can’t advise.
One of my clients uses Visual Form Builder for their custom form.
Be aware that themeforest is a marketplace. There are thousands of free themes here in the WP repository.

You say

what WP does best (serve many similar pages from a database) is just what I don’t have any need for,

but also say

I will need the style/appearance of the order form to match the rest of the website.

With WordPress powering more than a third of the web sites out there, I’m sure it can handle your case too. As I said, WP doesn’t do the front end. You have the theme and plugins for that. Having a consistent color scheme, menu, footer, and sidebar is good for the user experience, and so it’s good for SEO as well.
There are many sites that have no Posts, just Pages.