Yes very possible as long as you have verified no Enterprise features are actually in use.

But that being said some enterprise features became available in standard edition from 2016SP1.

The only...

The problem with creating indexes on the subscriber is that if you ever did failover to it for DR purposes, then all your CRUD statements in the app are going...

The log chain doesn't break as the way availability groups work is to ensure the LSN's match between all replicas, so there is never any drift in the chain.

With that...

Use powershell and dbatools

get-dbauserpermission will do exactly what you need

What if you cannot remove the replica from the group?

If you have multiple databases in the group then removing the replica will affect them all, not just the database which...

You need to unload and reload the counters.

Plenty on the internet with a quick search for this.

Heres one from Pinal https://blog.sqlauthority.com/2014/11/07/sql-server-performance-counter-missing-how-to-get-them-back/

We implement CIS and have AOAG's the SA account is fully disabled and we dont get the error.

What was the implementation path, did you do the AOAG's before applying CIS. ...

The instance name yes you can use the same.  The same Virtual Name no

EG your 2014 instance is MySQLVirtName\Prod1 and you build a new 2019 instance of MySqlVirtName\Prod1 will not...

Size the database as best you can and keep an eye on it for adding more space when it gets below a certain threshold but would still have auto grow...

Restoring the database flushes the cache so the first time you run the proc your having to pull all the data back from disk.  If your talking multiple 100s of...

Also speak to your network security team they may have introduced firewalls between the servers and also the windows team if they have enabled or restricted the windows firewall

May need to start the dbmail process sometimes it’s a bit funny and will refuse to auto start when mail items hit the queue.

sp_start_dbmail

PBI can link to certain parts of SSRS reports, gauges, datasets etc, don’t know if it can link to a whole report though.

If you want MFA you will need to...

You should really be keeping things insync, so I would do both nodes at the same time.  You never know what will happen so if a patch fixes a bug...

Maybe able to do it with an application proxy, https://docs.microsoft.com/en-us/azure/active-directory/app-proxy/application-proxy, but I would be going down the PowerBI route now instead of SSRS, it gets more love from Microsoft and...