Whatsapp backup new cell phone?

I just got a new phone (changed from Samsung Galaxy S7 to Huawei P30 lite)

and always make my WhatsApp backups in the WhatsApp app via GoogleDrive including pictures and videos.

So does that mean that my old group chats and private chats on my new cell phone also look like my Samsung? So all chat histories from previous years are still there with all pictures and voice messages?

I'm very attached to memories and just want to be on the safe side.

And how exactly do I activate the backup? Can this be done using the old SIM card or the Google account?

If you always saved everything, yes.