These maps are free to use if certain conditions are met. See the license!
At least for me they look out pretty good. See a screenshot:
How to download and make edits:
Press "share" icon. You get a dialog which allows to select file format and the wanted map area. The area can be presented as numbers or you can draw it onscreen.
One of the format options is JPG, but nobody wants JPG artefacts to his map before he has inserted his own data. Forget it.
SVG version unfortunately was a mess. Illustrator showed some unrecognizable jumble and Inkscape freezed under the load.
PNG was usable. Pixel dimensions were not freely selectable, but I got it out about 2000 pixels wide and high, when I input the scale 1:1000. The webpage adjusted it to 1:1900, bigger size wasn't available.
Most drawing programs open PNGs and allow editing.You can add markings and comments to a PNG also with office programs such as PowerPoint. Insert the image to a PPt dia and draw & write what you need.
PDF was openable for edits in Illustrator. Due a missing font unfortunately the texts and the underlying "contrast enhancing outlined text shapes didn't fit". An Illustrator guru probably would use the PDF anyway, but that's not beginner's job.
Another way to make edits to the PDF is to use a specific PDF tool. Even Adobe Reader is OK, if you are happy with those rudimentary edits which are possible with the commenting tool. I think that this is your case. Adobe Reader was even able to make the texts and their underlays to fit.
More edits to PDF are possible with Acrobat or Foxit Fantom. They are not freeware like Adobe Reader.
PDF and SVG both presented much larger areas than the selected area, only some details were ignored in the unwanted area. That slowed down the computer.
For small areas even a screenshot can be useful.
Conclusion: Try PNG or PDF