Also, I think the VPN service we choose will also affect the internet speed.
It depends, most of the time VPN is just use to hide your identity or simply do an anonymous browsing by using different IP. I’m not how can VPN increase the speed if the internet source itself has a capped speed on your country.
The only time I experienced that VPN increased my browsing speed is when it bypassed the speed limit set by the ISP provider but in general the speed is already there, the ISP is just capping it on some internet promo.
So I’m not if VPN can bypass an original slow speed internet.
Not all VPNs help us increase our internet speed and people are right when they say that most VPN usage will slow down our internet. But there are some cases where VPN can help us speed up access to certain websites. I am not an IT expert and I did not just hear it from others, I experienced it firsthand. There were times when my country's international internet cable line had problems which slowed down the internet speed a bit and using a VPN helped me solve the problem.
The current VPNs I am using are Express and Nord VPN, both of which are paid VPNs. In my opinion, using Express and accessing the recommended servers will improve internet speed somewhat but Nord does not.
https://surfshark.com/blog/do-vpns-slow-down-internet