I have no real idea. But have you set AJAX in Settings → Administration - > Basic Settingshttps://cloud.server.tld/settings/admin
I think the reload of config.php is sheduled from AJAX. Perhaps you must wait and execute some Nextcloud actions.
It is not a good idea to run Nextcloud “in a hosted environment” … with … “no root access” (or shell access from another user). Search for Managed Nextcloud for small money (or free) or for hoster with shell access.
Yes. You do not need root access. You need shell access to the webserver/nextcloud user.
Then you can use all occ-commands, too.
In that case your system is also well suited for nextcloud.
But you can also look around for Managed Nextcloud.
I use self-hosted and Managed Nextclouds, too.