Hi and welcome!
This is a new change so of course this is going to be a challenge and stressful for your dogs. Once you get access, go to the training section and check out the two week shut down sticky. It is a good, smart way to integrate new dogs with each other that better sets them up for success. Not sure how long your new pup has been with you, but it probably isn't too late to give it a try
Your pup is one year old. Congrats, you have a brainless teenager! This is the worst time of their life. All training they have gone through goes out the door. I have trained both my pups since youngsters and as soon as they turned into teenagers it was like I had never done any work with them. It feels like you're starting from scratch. It's probably a combination of newness, excitement, and the age that you are dealing with.
Your number one ally in this battle is exercise. You need to tire your crazy teenage pup out. Some long walks, maybe a run, hikes in the hills, playing some fetch... if you do this daily everyone in your house will be happier - including your 10 year old ridgeback. This one simple trick could change the vibe in your home dramatically.
Aside from the physical exercise, you need to mentally stimulate that crazy pup. Maybe a work to eat puzzle, or feeding them their kibble through obedience. Sit = piece of kibble. Down = piece of kibble. Work for that food! They also sell devices that work their brains. Here is a video of my girl using her work-to-eat toy for the first time.