Advice needed on shipping items from Japan back home to Canada

Hello and thank you for taking the time to read this.

I know this kind of question has been asked hundreds or thousands of times before but a lot of the information is either outdated or contradicting itself by now and I would like to get as much information as I can that is directly relevant to my current situation as of right now.

I'm a Canadian citizen currently travelling in Japan with only a few days left before I head back home.

I would like to know as much as possible about shipping items back home so that I can make some space in my luggage for souvenirs.

Note that the general recommendation of "buy another suitcase, fill it up and check it" is likely not the best option for me since the cost of buying a bag and paying the extra fee(s) for additional checked bags is likely to be higher than shipping items back and sticking with my current luggage for souvenirs – the reason being that my flight within Canada (west coast to east coast) does not currently include any checked bags and those fees are very high on Canadian airlines!

So, I want to ship a large-ish box back home so that I can stick to my current luggage on my flights. If I'm misguided on this I'm glad to hear it but please don't assume I haven't already considered it.

Now, I want to know:

Can I fill a box with my own belongings and ship it back home so that I carry the souvenirs with me, without worrying about paying customs for my own clothing, shoes and some accessories (laptop, camera, Xbox controller, umbrella)? That is to say, these are items that I brought with me to Japan and were paid for a long time ago in Canada. I don't have any receipts or proof of purchases for them, but I bought them IN CANADA and paid taxes on them. Will customs want me to pay fees to ship them back home? Or is this done often enough that it won't get flagged and allow me to do so without paying customs on things I'm technically not importing, just sending back to myself to avoid carrying them? Is there anything specific I have to do in this scenario?

If not, what would be the best route for me to go? Ship the souvenirs (keeping in mind restrictions on prohibited items, of course) and simply paying any relevant customs on them at delivery?

Any advice that can help me out here is going to be highly appreciated.

Thank you again for taking the time to read this and helping a clueless traveller who just wants to make it back home with as little hassle and extra costs as possible.