Which information a site can get when scraped by a scrapy spider?
The site owner can see this info.

Spider name. You can change the to anything you want
IP address you can use a VPN or proxies to change it.
Browser you are using. To change this go to settings and go look for USER_AGENT
remove the comment and you can easily go on google to search for other user-agents.
Cookies. Scrapy has cookies enables by default. Go to settings and look for COOKIES_ENABLED Remove the comment so it is set to False. This would make the scraping job more stealthy.
Concurrent_Requests. This is so also in the settings. It is how many requests you make simultaneously. It is better to lower the number so it is more friendly to the website.
I have a Single file spider which crawls only a site. Which informations can the owner of the site can see? 
Here, I am not using custom settings. (So that's default setting).
Example: 
1.Spider name
2.IP
3.OS