macOS Alternative to Windows Photos App

There are a few ways to approach this.

1. Learn how to use Photos. it's a lot more flexible and powerful than just having folders in the Pictures Folder. It has albums and smart albums, and powerful processing and editing tools, plus you can share your images across your devices effortlessly. But you have to accept that it is a database, and data has to be imported to it. So you can import your folders into it and then see them there. There's a lot more to it that that, of course, and if you want to explore that option, let us know.
2. You have a simple image viewer built in to the OS - icon view in the Finder. That, plus Quicklook, is enough for some folks. To see quicklook in action simply click on an image file and tap the space bar to see the image file full size. Use the up/down/left/right arrows to navigate through a folder of images.
3. Use a dedicated Image Viewer - that is an app that shows you the images and little else. There are hundreds: but I think PixlPath is pretty good. (https://apps.apple.com/ie/app/pixlpath/id6445800950) or, there are some editors that have Image Viewers built-in, like Graphic Converter. (https://www.lemkesoft.de/en/products/graphicconverter/)

I think the best option is to check out and learn Photos. It's immensely flexible, it's efficient and one you grasp that its a database and not a file viewer you're half-way there.

If you drag a folder of pictures into Photos, then you see a page of potential imports for selection, and at the top

you can check to Keep Folders. Then folders of pictures will become what in Photos are called Albums, and albums will be in folders.

To work as it should, Photos imports pictures to its Photos Library where it can scan them and keep track of their thumbnails and stuff. So after you Import the pictures to Photos, you can send those Folders of jpgs to an external drive for archiving, and you can remove those from the Mac's drive. All the pictures are in the Photos Library. And Photos is a non-destructive editor. If you edit or crop a picture, maybe cutting off the sides or intensifying the color, the original file is never touched. Instead, your edits are stored in the Photos Database. 

At that point you stop thinking of pictures as Files, and you think of them as Images. Photos is not a File Manager, it's an Image Manager. This is is the source of the great power of Photos. A File Management system like Finder relies on filenames, file created dates, file modified dates, file extensions, and so on. In Finder you can sort files in folders using those file attributes, for instance, but not by content, since the content of a spreadsheet file is so different from an image file.

None of that is useful in Image Management. Pictures have similar content, and so their management depends on Capture Dates, Titles, Captions, Faces, Keywords, Objects, Locations, text, and things that are parts of  pictures but that aren't in files at all-- and there are lots of organizing options in Photos using those image attributes. Since pictures aren't necessarily in files, then sorting pictures by file date or file name doesn't make sense. Sorting by title or capture date, for instance, makes more sense, but that's not available in a File Management System.

At first, using Photos instead of Finder may seem a bit puzzling if you expect it to work like Finder or Explorer, but we can help.

So having my photos available in a file format, is important.

And simple: Select the file you want in the Photos window and go File -> Export... again, lots of options about size, quality and formats available.