Since BYOIP and BGP are your biggest requirements, I'd check those first because not every VPS provider supports them.
For the specs you're after (2–4 vCPU, 4–8 GB RAM, NVMe), you shouldn't have much trouble finding providers that fit. The network is probably the most important part here, especially if low-latency routing is a must.
I'd also check what kind of IPv6 allocation they offer, the quality of their network, and whether there are any extra charges if you want to bring your own IPs.
As for Rightservers, I'd make sure they support BYOIP/BGP and test the latency from the locations that matter to you before committing. The specs themselves aren't hard to find, but I'd pay more attention to the network and routing since that's usually what makes the difference for this type of setup.
