installation – Root Directory for multiple instances

I ve setup a new SQL Server 2019 and the default root path (during installation) was left at c: drive. Changed all the other paths for user-data-log files as well as tempdb and backup to different drive.
I was asked later on to add a new instance and by running the installation again stack to the point where I had to choose the root path for the new instance. First try was to let this one at c: too (and so I did) and again change the other paths to a different drive.
Outcome was the initial instance afterwards couldnt even be started from services and of course in Management studio no user (SA, custom one, NET Services/Current_adm) could login.
Thankfully, I had kept a yesterday backup of the whole OS and revert it back. This time I tried to set the root path of the new instance (second one) at a different drive than c: and it worked meaning that both instances could automatically start (in my previous attempt they couldnt only the new one) and in Management studio all appropriate users could login as well.

So my question is
-In case someone wants / has / need to let the second instance root path to c: drive also, does he have to change the folder the binaries are going to be installed? because below root drive there were 2 more paths greyed out c:/……. for the shared resources. Maybe this was my problem, that I let the second instance at c without changing the path?

-Even though I dont think so, is there going to be a performance issue having sql binaries installed again for the new instance? Do they need to be shared and not installed again? Talking about the Binn , Install folder and the sql_engine_core_inst_keyfile.dll

Thank you in advance