>>212093377
>which one should I use?
The one you like the most
>should I pronounce S at the end of words as an s-sound or an sh-sound?
If I was a gringo I would prefer S, because the sh-sound is very regional from Rio, Recife and the Amazon region.

>>212093526
>Is the Rio dialect the one that also uses the more guttural-sounding R?
Yes
>Also how common is the English R pronunciation?
It's spoken in the middle of the country, somewhat common
>I can easily pronounce it with the Spanish R too since I speak a lot of Spanish but I think my brain would confuse Portuguese and Spanish if I pronounced it that way.
You do what is the most natural to you

You will be understood anyway.

This map is showing all of red as "guttural" but it's actually more close to /h/ outside of Rio, so I would say "aspirated". If you decide to speak like TV people, most news anchors and dubs pronounce the R in coda as /h/ and S as /s/