i just mentioned it because it beats handwriting out theme I and theme II. you can use this 'shorthand.' here's the six cpe bach prussian sonatas all together. i'm looking for the one in f minor to compare:
https://imslp.ca/images/imslp.ca/5/52/CPEBachPrussianSonatas.pdfand, perhaps a haydn sonata, as you suggest. we can see the things that are borrowed. cpe bach began the tradition of highlighting melody and harmony - and allowing feelings to be explored. the 'sighs and cries' also figured their way into haydn's sonatas - although - as you say -they maintained some of the cpe bach tradition of not being in what we would consider 'traditional' (which seems strange because that's the tradition) sonata form.
from hanning's 'concise history of western music' on page 313 it says 'in the baroque era, sonata generally meant a multi-movement work for a small group of instruments, most often in trio texture. in the classic period, the word had different meanings for different composers, two of whom we will study here - domenico scarlatti and cpe bach; it also connotated a compositional procedure or form, first articulated by the german theorist heinrich christoph koch (1749-1816).'
skipping to the part about cpe bach... 'german composers, though not the originators of the sentimental style (empfindsamer stil) began introducing it into their instrumental music toward the middle of the century...in 1742, cpe bach published a set of six sonatas (the prussia sonatas) and in 1744, another set of six (the wurttemberg sonatas). these sonatas were new in style and exerted a strong influence on later composers. his favorite keyboard instrument was not the harpsichord but the softer, more intimate, clavichord, which had a capacity for delicate dynamic shadings. the last five sets of cpe bachs sonatas (1780-87) were evidently written with the pianoforte chiefly in mind.'
'the main technical characteristics of the empfindsam style, of which cpe bach was a leading exponent, are apparent in the second movement, poco adagio, of the fourth sonata from his sonaten fur kenner and libhaber (sonatas for connoisseurs and amateurs; composed in 1765) it begins with a kind of melodic sigh, and singing motive ending in an appoggiatura that resolves on a weak beat, followed by a rest...while ornaments are abundant, they serve expressive rather than merely decorative ends. *much like the ending before the fermata in the sonata of beethovens -ending on a weak beat with a kind of sigh.
'the empfindsam style of cpe bach and his contemporaries often exploited the element of surprise, with abrupt shifts of harmony, strange modulations, unusual turns of melody, suspenseful pauses, changes of texture, sudden sforzando accents, and the like. the subjective, emotional qualities of this empfindsamkeit reached a climax during the 1760's and 1770's.