Hello @r0zbot, welcome to the forum!
You’ve got a number of things listed there that it sounds like you might be concerned about but only a few specific questions so hopefully we cover everything your wanting. 
I believe the “Cannot open WMI provider” and “Cannot find any MS SQL Server instance.” are both notification messages and can be ignored unless you really do have Hyper-V or SQL Server installed.
The " ```
The supplied option --default-filters is not supported and will be ignored" warning is telling you that parameter has been deprecated. Unfortunately, it doesn’t tell you where to look for the replacement which is now in the"Exclude Filter Group" feature (Release: 2.0.3.5 (canary) 2018-04-13). This may also be why the file scanning too longer after the update (it started including previously ignored system files.)
As for the --no-backend-verification=true parameter, that should do what you want so I’m guessing there’s a different step causing the slowdown that isn’t logging itself correctly.
While a larger block size would likely improve performance (fewer database records) that is one of the few parameters that can’t be changed once a breakup has been created. 
Breaking your backup into smaller chunks would probably give you a better performance boost, but of course that means starting over so it’s kinda painful.