I have been invited for a citizenship ceremony but had work travel planned for 3 days afterwards, since we have to cut up the Resident Permanent card, what are my options for returning back to Canada?
Would it be safer to go to a land border crossing upon return and show other documents?
If you can travel to a land border crossing, you should have NO PROBLEMS entering Canada. As
@masood8 commented, there should be no problem entering Canada.
The potential problem is boarding commercial transportation coming to Canada.
Canadians will be allowed entry if they arrive at a Canadian PoE. Technically the traveler needs to establish identity and status as a Canadian, but with rare exceptions establishing identity will facilitate CBSA's effort to verify the Canadian's status (once the traveler's identity is verified, CBSA can readily see that individual's status as a Canadian in GCMS).
Thus, generally, even a foreign passport will suffice. Will often go more smoothly, and quickly, if the traveler has additional documents to show status. Thus, yes, the citizenship certificate or, for those who wisely put the original into secure, safe-keeping, a copy of the citizenship certificate in conjunction with a foreign passport should facilitate a relatively easy PoE experience.
However, Canadians (both Canadian PRs and Canadian citizens) need to present prescribed documents to commercial carriers in order to board commercial transportation destined for Canada. In particular:
-- Canadians who are Permanent Residents of Canada need to present either a valid PR card or a PR Travel Document
-- Canadians who are citizens of Canada need to present either a valid Canadian passport or a special Travel Document for citizens
There are exceptions. U.S. citizens for example.
ALSO BE AWARE . . . Canada is still imposing a mandatory 14 day quarantine for international travelers. There may be exceptions, but most will be subject to this, and the fines for breaching the quarantine rules are fairly hefty.