Hello,
you can create a limited sitemap - with "Maximum depth" or "Maximume URLs" option limited so that it would gather about 20-30,000 URLs, which would be main pages representing "roadmap" sitemap for search engines.
The crawling time itself depends on the website page generation time mainly, since it crawls the site similar to search engine bots.
For instance, if it it takes 1 second to retrieve every page, then 1000 pages will be crawled in about 16 minutes.
Note, that is will take time to get your pages indexed in google, it depends not only on sitemap, but on many other aspects too, like number of backlinks from external sites.