This is not related to being premium or not. I have a website in Brasil for the past couple years on Cloudflare. It happens that depending on the ISP you are using to visit the website, it may or may not reach GRU/RIO in Brazil, or instead go through MIA/EWR/IAD etc. in the U.S.
From my base in Florianópolis, for instance, if I visit my site using Vivo Fibra, it is served out of MIA. But if I use my cell phone using TIM, the same website is served out of IAD. Sometimes TIM gives me GRU.
If you use WIndows Power Shell, you can check the long trip your ISP makes before handing traffic to Cloudflare by running the command
I use an iPad app on iPad called Nice Trace that gives a little more detail and even adds country flags to each step from my home to Cloudflare.
As you can see on the following screenshots, there’s some traffic in Brazil before it is sent to some Telefónica datacenters in Spain (Vivo) or TIM servers in Italy, and from there to Cloudflare in the US.
I doubt using Argo or Pro Plan would make any difference, as long as these ISPs continue to handle traffic the way they do now.