Yes, they are definitely fast enough for simple pages to a few thousand daily visitors. I've hosted dynamic websites from home using much more modest hardware and eventually used a first model Raspberry Pi for it.
Eventually I moved my sites to a VPS out of convenience. My ISP can't guarantee a static address with my current plan (although I've found it is static in practice so far), and the additional cost of a plan where they can exceeds the cost of renting a VPS.
If you have an ever changing dynamic IP allocation, you can still use Dynamic DNS services to update DNS records. I use GoDaddy for my names and AFAIR they provide this service, but there are also free providers that'll give you a subdomain, like https://dyndns.org. This requires some additional setup, because you need to update your IP with the dynamic DNS API regularly, for example via a cron job.
As for setup, if all you need is static pages you can use Raspbian and just install Apache or Nginx, put your files under /var/www/html and on your router forward some port to port 80 on your Raspberry Pi.