Very informative thread @Lewis, just spent a while reading through everything.
Personally, what I do does not require a large churn out of accounts every day so I'm happy to make 3-4 every couple of days manually. And as you can probably assume, I do this on my own IP through OSBuddy as if it were just another person making another account. I gave up entirely on getting past the locks (and buying accounts), because of some conclusion someone posted about a while ago.
For the life of me I can't remember where it was, but it was along the lines of what you were saying here
I bookmarked the service they provided, so as an example, here https://www.maxmind.com/en/geoip2-precision-insights
I think there definitely can be a science to this, I've done my own testing aswell, but there are a shitload of factors you have to consider and it's great that you're going through them in a systematic way. Don't listen to half these twats that aren't even reading anything before they open their mouths. I'm sure you and @sudoinit6 could find a solution between the two of you.
Speaking of, that problem you posed with the two machines with different success rates, that really threw me off. As if there is some sort of internal factor on your machine effecting it, more room for incompetency/lag maybe?
Either way, respect the hu$tle. Keep at it.