It means I can use SSL from cPanel without using SSL services from any companies?
https://documentation.cpanel.net/display/ALD/Manage+AutoSSL
Your host will have to enable AutoSSL for you. Then specifically choose Let's Encrypt.
Which SSL providers is better, Comodo or Rapidssl or Namecheap? I tried Comodo in the past but its pretty complex when using their services, no experience with Rapidssl and Namecheap and needing a review from you for this service.
All SSL's are the same regarding security. The only difference is the visuals - some companies provide seals, while others do not.
EV SSL's have a green address bar (additional screening). OV SSL's do not - but have some additional screening - issuance time for both is usually longer (days) than the standard SSL's (minutes to hours).
Comodo is an independent company. Symantec owns Geotrust, Thawte, and RapidSSL. The other paid SSL providers are GlobalSign and Trustwave
Comodo is generally the cheapest, with Symantec being the most expensive. GlobalSign and Trustwave are somewhere in the middle. Thawte is slightly more costly than Geotrust.
The only reason for choosing a paid certificate (IMO) is for EV/OV. The only reason for choosing Symantec is their little seal which is the most recognised.
My personal recommendation - if you want a paid SSL - go for the cheapest.
