AFAIK “renewing” your mortgage when the term is up is pretty much a formality. Of course, you’ve had up to several years of regular payments, so a credit history and more equity in the house. I have never heard of anyone getting a re-assessed creditworthiness during renewal, but don’t have a lot of personal experience, my current house is 80% paid off after 14 years and my previous house I paid off within 7 years. (I assume if you consistently miss payments, you may need to have a discussion with the bank…)
Generally, there is a simple assessment when you first buy a house - are you entitled to a mortgage or not? At the time, unless the down payment is more than 25% (I think?) you also buy CMHC (Canada Mortgage and Housing Corp. - government corporation) mortgage insurance, so the bank is guaranteed to recover any money they lose should they foreclose and the house does not sell for the principal owed. To qualify for the insurance, the CMHC requires a down payment of 5% (I think?) and discourages borrowing that down payment. So there is a shortage of high-risk, no-equity home buyers here. Similarly, the bank assumes no financial risk, just the hassle of dealing with any delinquent customer. If CMHC won’t give the buyer a mortgage, a bank would be stupid to assume that risk themselves - so they pretty much don’t.
you either qualify or you don’t, so with the insurance the bank does not have to charge different interest rates depending on credit scores. I think there’s a specific criteria in the contract, when your mortgage is considered sufficiently in arrears that the bank can foreclose under the terms of the CMHC insurance, and so collect if they can’t sell for a high enough price. Other than that - you simply renew for the published rate.
If you qualify, you get the published rate. Choose your term. When it’s time to renew, get the current published rate, choose your term - or find another bank who will be happy to take you. IIRC the CMHC insurance is for the life of the mortgage itself, not just the term. It is possible to negotiate and maybe shave a few fractions of a percent off the published rate, especially if you bring other business (like a big retirement savings) to the same bank.
Until the last few years, general thought was interest rates would be going up soon… So the variable rate was lower than the fixed rates, and interest rates are generally higher the longer the term. When I locked in with 5-year fixed in 2019, I got 2.74%, slightly better than the published rate; before that, variable had been consistently less. 10-year is rarely worth it unless you think interest rates will jump crazily in the next few years. (Canada’s prime rate is generally within a fraction of a percent of the USA rate.)
So like the USA, the banks assume less risk than the government does. Same thing only different. In general, the CMHC insurance premiums make the process self-financing unless there is a serious market downturn. their rules also AFAIK disallow mortgages where the principal is not being paid down.