@fabricioavil For the dreamcast you can easily convert tracks to chd, this will save space and make one file fore every game. This link should help https://www.reddit.com/r/RetroPie/comments/72kh6q/stepbystep_guide_how_to_convert_sega_cd_or_pc/
As for scraping all the dos games, im not going to lie, it will be a pain in the rear. Shell scripts will scrape like any other rom. Many of the dos games on screenscraper.fr do have shell scripts associated with them; but CRC checksums will likely vary. I use Unversal XML, which will at least create an entry for every game, making it easier to fill in manually. Setting it to check by file name only will help, but it will have to match pretty close.
In my experience there has been no system that scraped pefectly, there is always a game being missed when it shouldn't, wrong box art, and so forth. So I have had to take a machete to every gamelist.xml (except for neogeo pocket). But it gives me something to do while the Lady of the House is watching America's Got Talent.