I think one of the links that can usefully be made between these two Modernist texts is the way that both authors explore customs and behaviour of the Edwardian society. Clearly this is more evident in A Room With a View, but we can draw some interesting parallels with "The Open Window."
If we examine the character of Lucy Honeychurch, it is clear that she is a character who is not yet fully "formed" in the Edwardian sense of the word. She is desperate to "fit in," practising statements and bows, and wants to be accepted by society, becoming a social mover and shaker by marrying Cecil Vyse. This is of course why she is in Italy at the beginning of the novel, so that this finishing process can be completed, with Miss Bartlett playing the role of her teacher. Of course, we are already given evidence of the cost of "fitting in" as Lucy tells Cecil that she was prevented from bathing in the Sacred Lake along with her brother. Of course, it is the Emersons, a family who do not "fit in" and are very happy to not fit in, who show Lucy that to be a slave to such social customs is actually to betray your deepest self and to risk becoming little more than a programmed robot. Lucy is thus able to reject the conforming force of society and be true to her own emotions and desires by marrying George Emerson.
Of course, social customs are evident in "The Open Window," as Framton Nuttel has been given letters of introduction to all the best families of the society he is visiting and is met politely by Vera whilst he awaits her aunt. Note how Framton Nuttel is depicted as he faces the "self-possessed youn glady of fifteen":
Framton Nuttel endeavoured to say the correct something that should duly flatter the niece of the moment without unduly discounting the aunt that was to come.
Behaviour is dictated by the customs of Edwardian society, as Framton Nuttel tries to "fit in" during this "formal visit" where he is expected to act in a certain way and say set platitudes that are demanded by society.