Hi Jacqueline. I get this question a lot and so I wrote a pretty large guide/article explaining the different approaches, what I used to do, and what I do now (plus the pros and cons of each). Here is the article for you:
https://www.buildwealthcanada.ca/what-investments-to-hold-in-an-rrsp-vs-tfsa-vs-taxable-account-asset-location/

Also, I link out to it and lots of other frequently asked questions and answers from course students here:
https://www.buildwealthcanada.ca/etf-index-investing-course/16-additional-tips-and-conclusions/
Regarding your other question: When I was in the accumulation stage, yes, I would buy the same ETFs once a month. I would use the rebalancing spreadsheet in the course to determine which of the ETFs were currently underweight. Then I would use that spreadsheet to know how much of each ETF to buy with the new money from the job so that when I was done doing the purchases, I would be balanced once again (or at least very close to being perfectly balanced).

This is a very cost effective approach too because by rebalancing in this way, you don’t really have to sell to rebalance at all. You just top-up the ETFs that are underweight with the new money that you are putting in. In this way, you don’t end up paying any commissions in Questrade because you are buying ETFs (which is free), as opposed to selling ETFs (which they charge the $5 or so commission per trade).

FYI: This stops working as well when we have major declines in the market (like the 30% drop we saw when COVID first hit). But, apart from those rare occurrences, you can usually keep your portfolio in balance by just buying the underweight ETFs.