He is one of Japan's foremost pianists.
This region is known as one of the country's leading rice-producing areas.
This hot spring is known as one of Japan's leading hot springs.
He is one of the top engineers in the industry.
一流 describes something as 'first-rate' or top-tier in quality, while 屈指 specifically ranks it among a small, countable group of the best in a category.
抜群 emphasizes standing out remarkably from the rest (often used predicatively, 抜群だ), whereas 屈指 is used attributively (屈指の) to mark membership in an elite few.
卓越 conveys outstanding excellence or superiority in ability, while 屈指 focuses on ranking among a limited, countable top group in a field.
屈指 means 'one of the top few' without claiming the single top spot, while 随一 specifically means the single best.
From the literal meaning 'bend one's fingers' (屈 = bend, 指 = finger), referring to counting something on one's fingers, hence 'so few that one can count them on one's fingers' → 'among the best, leading'.