It also depends on what the goal is. If you need to extract some data from a specific site (as opposed to obtaining faithful representations of pages from arbitrary sites like a search engine might need to), then SPAs might be the easiest targets of all. Just do some inspection beforehand to find out where the SPA is loading the data from, very often the easiest thing is to query the API directly.

Sometimes the API will need some form of session tokens found in HTTP meta tags, form inputs, or cookies. Sometimes they have some CORS checks in place that are very easy to bypass from a server-side environment by spoofing the Origin header.