Clock setting is done on the controller E1. You do not need to re-enter this on the interface.
The interface serial 1/0:1 can be configred like a normal serial line. This means that you will need to specify the same encapsulation on both sides. However, this does not need to be PPP. The default (HDLC) works fine also.
It depends on the sort of E1 service you have. If it is a raw unframed E1 service, simply configure one side with 'clock source internal' and the other with 'clock source line'. If it is a channelized E1 service, you may need to configure 'clock source line' at both ends. (Note: 'clock source line' is the default so you don't really need to configure it).
On the resulting serial interface, HDLC encapsulation will be used as default. While that will work quite well, you can configure 'encapsulation ppp' on both sides too...
usually clocking is done by the SP, so "clock source line" would be ok.
The serial interface needs no more additional clocking statement, the controller configuration takes care about it.
Regarding PPP: you should use the same settings on both ends of the E1. The Cisco default is HDLC and as long as both sides are having the same setting this should be fine.
In case your E1 connects to a non-Cisco device, probably "encapsulation ppp" is not a bad idea, as this is a standardized Layer2 protocol, which should be interoperable with standard compliant equipment of any vendor.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...