i need advice if any can be given!

So i have three dogs in my household, the oldest is basically my dog. he’s a shihtzu mix and 5 years old, he’s a pretty relaxed and doesn’t potty in the house or rip up anything but the only problem i have with him is his barking. we have our furniture placed in a certain way so the dogs are able to get up on the couch and see outside the window, and in my room my bed is right next to the window and what he does is sits there and barks and this has rubbed off onto the other dogs. he only will bark at people walking dogs, or if he sees a dog, he won’t bark at people just walking. i’ve tried like a bark collar but honestly i don’t like using it on either of my dogs, i can’t really take away them looking out the window since there’s windows everywhere. We also have a big backyard so that’s where they go to use the bathroom but there’s a fence and it’s my neighbors house which they have a couple big dogs and every time they come out they’ll bark waiting for my dogs and when they get let out they’ll just run along the fences barking at eachother so maybe they think it’s like normal? please don’t be rude i’m just trying to see if there’s any advice anyone can give me so i can at least be able to walk him outside without him barking at other dogs like a maniac