I thought this post looked a little lonely here so I figured I give it a try and give you guys a reply 
I am not sure at all if that is the case but it is very likely, the OPCache errors are occuring because there is a duplicate entry somewhere to the opcache .ini files which should be overall harmless and other than that the SSL error is the only one that is critical for you (from what I can tell)
I gathered some links below with some relevant information about the OPCache for others that are looking at this post
https://github.com/nextcloud/nextcloudpi/issues/416
There are some instructions in the GitHub issue and PHP Freaks of possible locations to look for duplicate entries. As NCP is progressing from Buster to Bullseye this is going to happen again, hopefully someone that has some time over can make a PR with a fix for it pre-emptively this time
About the access to localhost, is your local ip, hostname or ‘localhost’ added as trusted proxies?