1. No. You need a real CRON job. Something that triggers with site access will never work for backups. A long time ago we tried that (“Akeeba Backup Lazy Scheduling” plugin) but it was not working very well — and that was with a purpose–built plugin, not a generic pseudo–CRON system. Joomla's upcoming pseudo–CRON is the same as WordPress: great for infrequent, FAST (under 0.1 second) tasks, not for long–running tasks like taking a backup or sending newsletters to hundreds or thousands of recipients.
As I said, your best bet is using something like WebCRON. It's between 0.50 Euros to 7 Euros a year to schedule weekly backups, depending on how long your backup takes.
2. WordPress allows you to use the username and email address interchangeably since at least 2014 when I first got involved with it. Joomla doesn't. Between the two, Joomla is right as a matter or preserving user privacy. Plus everything else I said.
If you go to SocialLogin's GitHub page you will see there's an issues tab. You can check the closed issues. That said, the feature you requested isn't even in the purview of the plugin. Email is not a social network.
3. The problems with capital letters in table names (be it the prefix or the table name itself) stem from the way MySQL itself works on case–insensitive filesystems such as NTFS, FAT, FAT32, exFAT, HFS+ and APFS. It is not something that depends on us.
No, you will NEVER be able to mute the environment checks (that's what you refer to as “warnings”). They are there for a reason. The report things which WILL cause issues taking or restoring a backup. Last time we let lower priority issues, like the prefix case sensitivity, be hidden we got inundated with support requests about things we have already documented will affect your backup. Worse than that, we had people SWEARING there are no warnings — even though the Backup Now page always displayed them anyway — and sent us a backup log file which showed right there that the warning was displayed and the user ignored it. So, no, these are not going to be hidden.
Nicholas K. Dionysopoulos
Lead Developer and Director
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