Never done an E-visa, but might do one this time to save a full page in a passport that has only one or 2 blank pages left which I need for a new Vietnamese visa. Am I correct in the assumption that the e-visa does not entail a full page visa sticker, just the tiny arrival/departure stamps?And entering overland from Thailand only Poipet and Hat Lek, not Ban Laem, accept E-visas 

Yes. Your points above are correct. This is the official website. Any others you might see are likely a scam or agents that will charge you a fee.

 

https://evisa.gov.kh/

Yes to all.  You print out the evisa and give copy to the IO entering and leaving, the only thing that goes in your passport is the entry and departure stamps.

 

Since Camb visas take up a full page  this is a distinct advantage.