Hi.

I have some questions about modifying codes.

1. I wanna build a password protected obfs4 proxy sever with my VPS.
I don't need that much privacy in terms of MITM for this.
I just wanna know if it is ok to build such server in Tor network.

2.I wanna overrides some Javascript API with add-on. but...
I just tried this with latest Torbrowser. it seems like I can't overrides some API's.
Because same add-on I made worked on normal Firefox browser. 
I wanna avoid some fingerprint tracking recently discovered. 
Is there any reason to block overrides by add-on?
Or am I missing something?
I wanna know which is best way to do this. add-on or Torbrowser itself. 

Thanks.