Research depth
Discovery
How well the tool supports keyword, competitor, SERP, backlink, or market research before execution.
Copywritely
Moderate content-oriented research depth.
The SERP checker accepts up to three keywords, supports several engines/languages, and analyzes selected competitor pages for common words, bigrams and trigrams. https://copywritely.com/serp-checker/
GrowthBar
Strong keyword, SERP, and competitor research coverage.
The official page says GrowthBar scans hundreds of Google SERP results and offers 7 billion keyword suggestions plus competitor keywords, Google Ads, and backlinks: https://www.growthbarseo.com/