Hello - hope you are doing well. I am a LBD patient and if you don't mind will give you a bit of what it feels like from inside here for some of what you are talking about. Warning-I am told by my lovely wife that I take the long road to explain anything these days - so be kind:-)
For reference I am 59 and was diagnosed ~2 years back. I also have the Parkinsonism aspect which these symptoms started earlier.

My neurologists tell me that LBD is like a degenerative traumatic brain injury, With that in mind:
**A good psych dr with experience with treating dementia patients is a must. Many of us can use the help of some anxiety or depression meds. Some anxiety and / or depression can be a trigger for some less than desirable behavior.

Overtalking - this is one that I can identify with. For me - I can have a hard time following a conversation. When I think I have something to add - I often just jump in - no matter if someone else is talking. For me this is due to my forgetting what I want to say and feel I need to get it out before I forget. Other times I know in some social situations I don't do as well. It is getting more difficult to recognize emotions from peoples expression and voices.This makes it much harder to communicate.

With the mask wearing it makes it even more difficult since I cannot see the whole face.

Yelling - I don't have a big issue with this so far (and pray that I will be spared that part). When I do yell - it is like a trigger goes off and yelling starts.I think one o the main triggers for me is the feeling of being confronted. Which opens another can of worms. With it being more difficult to gauge expressions and tones of voice - I often mistake normal questions as being confronted. Then I will sometimes yell - but not for a long time. My more common reaction is to lash out but not yelling - just can be somewhat not a nice as usual. So far I have lashed out (yelled) to my oldest son and my wife. For stupid things really - but they sure got me going.

Sometimes I get frustrated because of not being ablate do things I was a Navy guy for 11 years, Army National Guard for 4 years and I was a. network engineering manager for 30 years in my secular career. Man the stuff I used to be able to do - which now I can't anymore. Or when I cannot grasp a concept or follow directions.

Having a routine has become important to me - don't know why - I used to be kind of a spur of the moment guy. Now I need a routine / schedule.

I don't do well with change. If an appointment changes times or if the Dr is running late - it really gets to me. Or if we are running errands (I don't drive - doesn't go well when you don't know where you are a good part of he time.

A big change for many is giving up the keys. I was lucky - I guess - in that respect. We had talked about me stopping driving in late 2019.
It is very hard to not make that decision and even harder to have it made for you.
In my case in early 2019 I had a full retina detachment (macula off). I have vision in that eye - just distorted and no peripheral vision which comes in handy when driving - so that made the no driving decision for us.

I do get frustrated as I used to do most of the driving. Now I am a full time passenger.

I bring up some of this extra stuff as food for thought to maybe think about how he/she is feeling about the changes they are going through. Maybe that will help in working on coping mechanisms for now and in the future.

What we do, how we act or react are many times things that we don't have full control over anymore. Please know it is the disease. Deep down - even if we can't express it -our love, caring and feelings are still there - if nowhere but in our hearts.

I know that most of us want our caregivers to know that we love them and appreciate what you do for us- even if we don't always recognize it or convey it.I am blessed with my wife to be with me during this journey - a journey for both of us. A journey for all of you that are caregivers / patients.

What I can say fro those that are still in the early stages - to start taking about things like communication. Look at your lives and think of the situations you are frequently in. Think of ways to work around communication issues. Only you and your loved one can dive into specifics. For us it was thinking about some common places like Church.
I am a retired Pastor so I am used to talking over people in that setting 🙂

Mayo has a GREAT program for folks - patients and caregivers. It is a several day program where both caregiver(s) and loved ones work together. They can help with planning and looking to the future to help identify areas of potential issues and to learn coping mechanisms for both patient and caregiver. You can work as more of a team.
One of the moderators might remember the name - I can't right now - imagine that!!!

2 words about living with dementia's - "It stinks" - for all involved.

I will leave you with a few items from the Mayo website -

Alzheimer's and dementia: Tips for better communication

To improve understanding in both directions:

*Be patient. Take time to listen and allow time for the person with dementia to talk without interruption.
*Learn to interpret. Try to understand what is being said based on the context. If the person is struggling to get an idea out, offer a guess.
*Be connected. Make eye contact while communicating and call the person by name. Hold hands while talking.
*Be aware of your nonverbal cues. Speak calmly. Keep your body language relaxed.
*Offer comfort. If a person with dementia is having trouble communicating, let him or her know it's OK and provide gentle encouragement.
*Show respect. Avoid baby talk and diminutive phrases, such as "good girl." Don't talk about the person as if he or she weren't there.
*Avoid distractions. Limit visual distractions and background noise, such as a TV or radio, that can make it difficult to hear, listen attentively or concentrate.
*Keep it simple. Use short sentences. As the disease progresses, ask questions that require a yes or no answer. Break down requests into single steps.
*Offer choices. Offer choices when making a request for something a person might resist. For example, if someone is reluctant to shower, you might say, "Would you like to take a shower before dinner or after dinner?"
*Use visual cues. Sometimes gestures or other visual cues promote better understanding than words alone. Rather than asking if the person needs to use the toilet, for example, take him or her to the toilet and point to it.
*Avoid criticizing, correcting and arguing. Don't correct mistakes. Avoid arguing when the person says something you disagree with.
*Take breaks. If you're frustrated, take a timeout.

If you would like to know what it feels like from in here on other topics I will do my best to tell you about my situation since everyones situation is different. If you have 10 people with a dementia illness - you will have 10 different sets of issues. There isn't a one size fits all.

Hope you will be able to find a few words in this to help you to at least understand a little from this view.

Peace
Larry H.