Performance Benefits changing Registrars and using Lightshot DNS Vs Route53

Who you use as your domain registrar has no bearing on performance.

The DNS servers used do have a performance impact. Free ones that come with your registrar may not necessarily be performant. However you can usually log into your registrar and point your DNS at whatever DNS provider you like.

As for Route 53 as a DNS provider, the DNS isn't as low-latency as a number of anycast providers out there, but Route 53 should be more resilient to flaky internet routes due to the way they distribute the servers. It would be very hard to find a situation where all 4 of the servers they provide do not resolve even if there are major outages on the internet. So Route 53 should be more reliable. If you use a high TTL it can help improve the average latency across visitors.

From what I can tell, Lightsail's DNS seems to essentially run on Route 53 but is just packaged in a way that should be familiar to people who are used to the DNS panels of various web/VPS hosts. Lightsail DNS gives you a few million free requests. Route 53 on the other hand doesn't give free requests but is much more versatile in what it can do (Geo/Latency routing, aliases from other AWS services, etc).

Chances are for a basic Lightsail server, the Lightsail DNS would be just fine.