I wouldn't worry about the handles being seen. Will the fridge doors be able to open all the way? That would concern me much more than whether someone who is not heading towards the kitchen, and we know nearly everyone will end up in the kitchen at some time, will see handles.

Personally, I don't think it's a problem seeing the refrigerator door & handles if the rest of the refrigerator is "built-in" so it isn't a mass of SS. (Yours appears to be built-in.) Note: It's not just the handles, it's also the doors - the doors must stick out past anything adjacent to them - walls, cabinets, counters, other appliances, etc. If you want to hide the doors, then you will need a 9" to 12" spacer b/w the wall and the refrigerator - 9" will work if the wall isn't too much deeper than the refrigerator + doors + handles and the door(s) can open into the doorway; 12" if the refrigerator door(s) won't open into a doorway. That "spacer" can be a 9" or 12" tall pullout pantry cabinet or broom closet or it can be upper + base cabinets.

I wouldn't/couldn't do it in my house, but is HAS been done. Here's an old post on it - [https://www.houzz.com/discussions/stain-floors-to-match-stairs-dsvw-vd~876622[(https://www.houzz.com/discussions/stain-floors-to-match-stairs-dsvw-vd~876622)

I like your inspiration. The price sounds reasonable to me but I would get another quote to compare. If the stairs bother you and the change is affordable I wouldn't worry about the ROI. ROI would depend on the condition of similar homes in your area and the cost of the new railing as a percentage of the total value of the home. Keep in mind that you will enjoy the change until you sell and the updated railings will probably help your house sell faster.