Combine .htaccess. ( http to https AND www to non www AND remove trailing slash ) extending normal craftcms .htaccess
Update 12/06/2018:

Tested now succesfully following version on my server

# Redirect www to non www
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ https://%1/$1 [R=301,L]

# Redirect http to https
RewriteCond %{HTTPS} !on
RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R=301,L]

# redirect /bla/ to /bla
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} (.+)/$
RewriteRule ^ %1 [R=301,L]