How to limit internet access to clients which are not from DHCP or PPPoE?

So....
Mikrotik is PPPoE and DHCP server, but if somebody set manually IP address, and set gateway IP of Mikrotik he will get internet access.

How to limit internet access only to DHCP or PPPoE clients?

if you use PPPoE, make sure the server does NOT have any IP addresses set on it. In that case, only PPPoE users will be able to use the internet. In case of DHCP it's more difficult, so use PPPoE

in case of DHCP, just set Interface ARP-mode to read-only, and check 'Add ARP for Leases' in DHCP Server

yes, but DHCP has more drawbacks, PPPoE is more secure anyway