Ok so when i try to change the file location no matter what i do, nothing happens can someone please help. I am on Windows if that changes anything. also i cant change the path i dont understand what other people are saying.
I found an interesting conundrum that may be relevant to everyone whose twitch WILL NOT LET THEM change the file path to their appdata location. See, at some point, Windows 10 decided to screw with me, and essentially duplicate my user account, rename the folder to (user_name).000 and make the original (user_name) obsolete.
From what I can tell, i you had this happen, the curse client that twitch uses has NO IDEA that your account should have a .000 appended to it. This causes two problems. One, it wants to save the installer to the obsolete user folder, but naturally cant, making it impossible to install the game. Two, It wont save an install location filepath it doesn't think it has access to, making it impossible to set it to the default filepath the minecraft installer uses.
So, that aside, here's my fix:
Go to %appdata%\roaming]curse client, open Minecraft.settings
Rename all paths to the correct username (the one with .000 appended to it)
This will now let you use twitch to install minecraft, because it will place the installer in that location and run it.
install using Twitch to the default location, program files (x86)\Minecraft
This ensures both Twitch and Minecraft have full access to the files instead of getting confused with which user's folder to search
From here, everything should run fine, no other settings to mess with other than potentially RAM
If anyone is still having these issues, I was able to fix mine. When setting the custom path it would not let me choose the path I wanted, so it turns out that the twitch client for some reason doesn't like some filepaths. I think the issue is actually related to the name of your windows user, cause in my case I have a few letters in my name that are not in the english alphabet, and I've had a similar issue before with android studio where my username broke a few installs.
So try to create a folder on the root of your C: drive and set the filepath to that, and it should allow you to do so and go through with the installation. This was my experience at least and I didn't see a similar solution here so it might fix it for you