It is not advisible to adjust the setting file in the core package directly sorry if my hint was misleading in that regard. You can add the values you want to override to Configuration/Settings.yaml . This is also where you can add the db settings (the installer is not really needed if you can write 5 lines of yaml.)
Regarding the error there is usually a php cli-binary in pathes like /usr/local/bin/php7-73-CLI (example from a crappy host i had to deal with). Be careful and make sure the php version the webserver uses is the same you configure and use via cli.
Also make sure to call flow on the cli like this /usr/local/bin/php7-73-CLI ./flow ... if you use cli commands.
Note: It may also make sense to use the path Configuration/Production/Settings.yaml if you are using Production context (you should if you like speed).