Bach's '2 Chorales' likely refer to chorale settings, a staple of Baroque organ repertoire, often featuring intricate counterpoint and harmonic richness. These pieces demonstrate Bach's masterful ability to transform simple hymn tunes into profound musical statements.
Mastery of counterpoint and precise articulation are essential for a clear and balanced performance.
2 Chorals is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of 2 Chorals lasts about 6 minutes.
2 Chorals is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.