1. Initial app download & unzip to machine
The only way to reduce the copy and extract part is to reduce the size of the project. You save time by reduce the number of files to extract too.
We are working with our cloud provider to provider a new storage system based on SSD to reduce copy and extracting process. Right now this feature is still in preview, but we have an early access on it so, we can try to provide you a premium storage, you should get better result with it.
2. App launching & loading
The start process depends on your application size too, the application runs on a SSD so right now there is nothing we can do to reduce the launching time of your application once the copy and extract part is done.
3. Asset bundles & Addressables with unity?
You can package the bundles in your application but it will increase the size of your zip file and increase the loading time before your app getting ready.
I think the best way to reduce loading is to put asset bundles on a remote server and download them.
4. Seperate Exe files in one zip?
Yes you can start an other exe from a hub app.
Hope theses answers will help you.