HISA ETFs are not too good to be true, they were a result of multi decade highs in policy rates. Banks could offer these rates of savings because of the Bank of Canada overnight rate. As rates continue to decline, the yields paid on these HISA funds will go down.
For example, you earn 4%~ on something like CASH.TO right now, however if the BoC cuts rates by 50 basis points in December, you will likely earn 3.5%.
If capital preservation is key for you, there are a wide variety of fixed income options available. You could build out a solid portion of your portfolio in bond funds if you'd like. The maturities etc would ultimately depend on your overall risk tolerance, obviously with longer duration bonds yielding more, but providing more pricing volatility.
The one key thing to understand with these HISA ETFs is there is no CDIC insurance, meaning if the underlying institution (in this situation with these HISA ETFs, mostly National Bank and CIBC) were to go belly up, your money would NOT be protected. A very small chance, but a chance nonetheless.