One of my favorite ways to audit Amazon ad accounts (fast):

1 - Export Search Terms Report from ad console

2 - Add columns for: % of total spend, % of total sales. This allows you see what campaigns are spending the most vs generating sales.

3 - Sort by % of total spend.

Now compare where you're spending vs ROAS.
Add in organic keyword ranks.

What to look for:

--> If a high % of your spend is going into low ROAS campaigns, you might want to reconsider reallocating budget to high ROAS campaigns.

--> If a high % of your spend is going toward keywords with good organic ranking, might want to pull back on budget and observe rank, then increase spend again if rank begins to drop.

Personally I've cut ad spend on keywords in top 10 organic ranking in the past with good results. Has lasted 20-30 days with maintaining rank and no ad spend. Of course, depend on how competitive your niche is too.