Hello!Please tell me how many sites can I add through your DNS, without compromising the speed of sites, on a free tariff?
You can have as many domains as you want. Free or paid makes no difference.
The overall number has no impact on speed or performance.
There are limits on the number of DNS records an individual domain can have, on free plans it is (last time I looked) 1,000, and paid plans can have 3,500. Enterprise customers can ask for that limit to be increased also.
There is a limit of inactive domains you can have at once. If you are adding hundreds of domains you will have to ensure the nameservers are set correctly as the domains are added.
Thank you very much for the detailed answer!