What is the difference between a sync for my team and a sync for the Jira site?

[Nathan Given]

Simple question, but ultimately I'm confused.  Details are below.  Any help is appreciated.

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Before migrating to the new Jira alerts, we had OpsGenie "integrations" for each team (and in Jira, there was a corresponding webhook).  This made sense to me and the webhook (in Jira) and corresponding integration (in OpsGenie) could be customized per team.

Now that we are part-way through our migration into Jira Alerts, I'm trying to figure out how to understand the difference between a sync for just my two teams, and a sync for the Jira site (and how to get our customizations back).

Here's our setup:

We're using JSM and we have two projects where we receive issues.  We generally have three priorities, "Normal P3", "Moderate P2", "Critical P1".  Within our company, we have over 25 different support teams that are responding to Jira issues and interacting with customers (we have hundreds of agents).  In Jira, the way we designate which team is responsible for which issues is through a custom field called "Support Team" (it is a select field with over 25 different options that represent each team).  Most (if not all) of the "teams" (read: values in the "Support Team" drop-down) had a corresponding "team" in Ops Genie and now show up as a "Team" in Jira.

Our Jira administrator setup two "site" syncs: one for each project.  These syncs are pretty generic ("if priority = 'Critical P1' then create an alert).  On both of these syncs, within the "Create alert rule", there is a "Support Team" property with a value of

{{customFields.customfield_11668.substringBetween("value=",",")}}

Since there doesn't seem to be an ability to filter a sync on a custom field, it appears that the way to get these newly created alerts assigned to the right "team" is to use the custom field property.

Thus, there is a policy setup for each team where "if value of `Support Team` in extra properties = "[my support team]" then modify the responders field to be the associated Jira team (the team names generally match the custom field values, but not always.

Okay, so, these two syncs and these global policies are generally working, except for my teams we have some slightly different needs (for example, we want to get alerted on issues that have a different priority than "Critical P1".  We want to receive an "Alert" when a "Moderate P2" issue is created/modified and the Support Team custom field has a value that matches a certain value).

If I create a team-based sync, how will that work?  Will JSM evaluate every "Moderate P2" ticket against my sync and create an alert for every Moderate P2 ticket?  I don't think I want an alert for every Moderate P2 ticket, I just want them when the "Support Team" custom field has a certain value.  (But not all teams want this setup).  Another customization: when the issue closes in Jira, for my two teams, I want the alert to be closed.  Another customization: when the issue is transitioned to "In Progress" in jira, I want the alert to be acknowledged.  (I'm not sure how many of these team-specific customizations we can setup, but we were trying to use a team-based sync since these are team specific, but we're unsure how a team-based sync is scoped differently from the site syncs).

I guess I just don't understand the difference between a sync at the on-call team level and how it differs (or doesn't) from a sync at the site level and how these interactions come into play with a "Support Team" custom field and how to get back the functionality we had with webhooks + ops genie integrations.

Apologies about the long post.

Thank you,

Nathan

PS: This suggestion makes me wonder if what I want to do is even a possibility: 

https://jira.atlassian.com/browse/OPSGENIE-338

PPS: Should I somehow be using an integration instead of a sync? Should it be a global integration or a team integration?  This is, unfortunately, confusing.  I'll keep reading up on this to see if I can figure it out.