Does battery amp-hour matter for circular saws?

Yes, more than for almost any other cordless tool. Reviewers across the Dewalt and Milwaukee subreddits repeatedly note that 2.0Ah packs bog these saws down, while 5.0Ah, 6.0Ah, and FlexVolt/high-output packs unlock noticeably more aggressive cutting. Plan to pair a cordless circular saw with at least a 5.0Ah battery.