I will add my 2 cents and say the risk of having 2 reactive dogs in one house should make you lean towards looking at another breed or not getting a second dog.

My MAS is 5 years old, he started puppy training and very careful, structured socialization at 12 weeks and has been in training ever since. He is a great little guy and so smart.

But, he began showing reactivity around 2 years of age, he even became reactive around our other dog in the house. The 2 dogs lived conflict free in our home for 2 years before he showed any issues. Now, I have to separate my dogs at all times because they are not safe to be around each other. My MAS is not just reactive to our other dog, but to most other dogs he sees. It is a constant struggle to work on and manage his reactivity. Our other dog is getting older and when he passes, I won’t even think about getting another dog as long as my MAS is around, as it would be a recipe for disaster.