How can I tell if a given EB plan is an H&W plan or fringe benefit plan?

The context I am familiar with those two terms and the difference is that 'welfare benefit plan' is an ERISA Title I term. If the EB plan is subject to ERISA Title I (and is not a pension plan), then it is a welfare benefit plan that needs to comply with ERISA Title I.

On the other hand, a fringe benefit plan is a tax filing term. As I recall, all welfare benefit plans would also be 'fringe benefit plans' for tax filing purposes, but an EB plan that is not subject to ERISA Title I (and thus not a welfare benefit plan) might nevertheless be a fringe benefit plan for tax filing purposes.

Until about 7 years ago, a small EB plan exempted from the ERISA Title I annual reports filings because it had under 100 employees and no trust fund, but would nevertheless have to make a tax annual report filing. I think it was April of 2002 when the IRS decided not to require such any longer.