The key of B major, as perceived by Bach, is indeed a remarkably calm and peaceful key. Typically, in a fugue, the theme modulates to related keys, and for a piece in a major key, a minor theme would appear several times. However, in this fugue, it appears only once in measure 24, with all subsequent themes remaining in major. Even this appearance in measure 24 is not particularly dramatic, nor is it at all serious. It passes by very quietly, without incident. Considering this, it might be a key with a character similar to Bach's E major.

This fugue features two instances of a transformed theme, known as inversion. Simply put, it's a theme that would appear if you read the original theme as if reflected in a mirror. The first instance begins on the upbeat of beat 1 in measure 18, in the soprano voice, starting on F-sharp. The other instance begins on the upbeat of beat 1 in measure 20, in the alto voice, starting on B.

These two instances should definitely be treated as themes and made clearly audible.

While dynamic contrasts must, of course, be applied throughout, in the case of this fugue, consider it less as a 'drama' and more as a sensation of being in a fantastical world, where quiet and pleasant time flows.