Is the element of 'suspense' in a novel considered more typical of popular or highbrow/classic fiction?
The short answer would be that most popular literature and some highbrow literature use suspense as a way of enhancing the reader's experience. But the reality is far more complex than that.
Many of the earliest English novels followed the conventions of the picaresque, a genre in which we follow the adventures of a colorful character. Although individual episodes may contain suspense, the focus is more on character. Novels by writers such as Defoe or Richardson were considered popular in their own period but are now standard elements of the school curriculum, a marker that distinguishes the highbrow.
In the early 19th century, popular Gothic writer such as Radcliffe, relied more on suspense than Jane Austen, whose works had a more leisurely pace and focus on character, but there are moments of suspense in Austen.
Serial publication of novels in the 19th century meant that most novels were plotted with "cliff-hangers" at the end of each installment so readers would buy the next issue of the periodical in which they appeared. This might be described as "popular" and certain writers, such as Trollope, explicitly eschewed it, but since George Eliot, Charles Dickens, Thakeray, etc. wrote for serials we can hardly dismiss the phenomenon as genre fiction.
In 20th century literature, there is more of a distinction between fiction that uses suspense and literary fiction, but even admired 20th century authors such as Faulkner and Byatt still employ suspense.