Postgresql – How to uninstall PostgreSQL (and pgAdmin3) from OSX Sierra

I've been having some difficulty getting up and running with PostgreSQL. Having uninstalled PostgreSQL with brew uninstall postgresql and uninstalled/removed Postgres.app I re-installed Postgresql.app. When initializing the .app I was still getting this error message:

Per Postgresql.app's documentation, I looked at my Activity Monitor and saw nothing named postgres or postmaster:

I found this helpful answer and after sudo find / -iname createdb discovered I had a createdb file living in /Library/PostgreSQL/9.5/bin/createdb who contents
include "pgAdmin3.app" which is no longer supported. (I am presuming I installed it when I first started looking into PostgreSQL and wasn't really thinking… whoops!) I also searched for pg_hba.conf files and found I have a postgres directory in my usr dir: /usr/local/var/postgres/pg_hba.conf

Is removing the Library's folder (/Library/PostgreSQL/) adequate for a complete uninstallation of pgAdmin3, or are there other files and directories to remove? For example, should I also delete /usr/local/var/postgres/? Any advice is greatly appreciated, thank you.

NOTE:
per pgAdmin3's uninstall site, ls -al /Applications | grep pgAdmin returns nothing.

per this similar question on another SE site, sudo find / -iname .pg* reveals nothing. Also, per the answer to that question, ~/Library/Preferences/ does not contain:
org.postgresql.pgadmin.plist.lockfile
org.postgresql.pgadmin.plist
pgadmin3 Preferences

per the comments in this answer it looks like I should remove the /usr/local/var/postgres/ directory manually. And from the question, I also invoked sudo find / -name "*postgres*" and got a whole bunch of listings. Of note, I see that BlackMagic's DaVinci Resolve is using a PostgreSQL server. The install timestamp of pgAdmin3 is the same as when I installed Resolve… ? Not sure what I need to do.

This forum conversation sheds some light on Resolve's PostgreSQL server removal.

UPDATE: per comments, when I launch Activity Monitor as admin:

sudo "/Applications/Utilities/Activity Monitor.app/Contents/MacOS/Activity Monitor"

…I see these processes associated with user:postgres

Should I quit these processes before deleting the contents of /Library/Postgres/... and other associated files like:
/Library/LaunchDaemons/com.edb.launchd.postgresql-9.5.plist

/Library/Application Support/Blackmagic Design/DaVinci Resolve/Prereqs/config_postgres.sh
/Library/Application Support/Blackmagic Design/DaVinci Resolve/Prereqs/install_postgres.sh
/Library/Application Support/Blackmagic Design/DaVinci Resolve/Prereqs/postgresql.zip
/Library/Application Support/Blackmagic Design/DaVinci Resolve/Prereqs/upgrade_postgres.sh

&

/private/var/db/dslocal/nodes/Default/groups/_postgres.plist
/private/var/db/dslocal/nodes/Default/users/_postgres.plist
/private/var/db/dslocal/nodes/Default/users/postgres.plist
/private/var/folders/gv/jzhl4n_j2gz6_hjvq4f2xq9h0000gn/C/com.postgresapp.Postgres2
/private/var/folders/gv/jzhl4n_j2gz6_hjvq4f2xq9h0000gn/C/com.postgresapp.Postgres2MenuHelper

&

/Users/<user_name>/Library/LaunchAgents/com.postgresapp.Postgres2LoginHelper.plist
/Users/<user_name>/Library/Logs/Homebrew/postgresql
/Users/<user_name>/Library/Preferences/com.postgresapp.Postgres2.plist
/Users/<user_name>/Library/Preferences/com.postgresapp.Postgres2MenuHelper.plist
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Aliases/postgres
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/check_postgres.rb
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/postgres-xc.rb
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/postgresql.rb
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/postgrest.rb
/usr/local/var/homebrew/locks/postgresql.brewing
/usr/local/var/postgres
/usr/local/var/postgres/postgresql.auto.conf
/usr/local/var/postgres/postgresql.conf

Maybe I can leave the Homebrew dir/files?

Note: found these with sudo find / -name "*postgres*"

Also per this github blog, should I "Restore shared memory settings" with sudo rm /etc/sysctl.conf