applied reesearchers gives my spells 1 less cost. but what if my spell has FLOW 2. do i pay 2 from trash? or does it also get the discount?

Yes — the discount applies to the Flow cost. Playing a spell from trash via Flow is still playing that spell; the Flow cost is an alternate cost that replaces the base cost, and Applied Researchers' discount then applies to the total cost like normal (Rule 829.1.c.1, Rule 356.4).

So for a spell with Flow [2], you don't pay the full 2 — Applied Researchers reduces it by [1] Energy and [1] universal Power, down to its minimum of [1]. You'd pay 1 Energy. The [A] portion of the discount only matters if the Flow cost (or other costs) includes a Power component.