Well, I wouldn't buy one unless it was returnable if it failed to work. I have put my own SD cards into my Garmins, and with considerable effort, used the (paid) map subscriptions to update them. That said, a Garmin running from an SD card has noticeable lags in "painting" the screen image, which can affect driver navigation. Older Garmins can be completely unable to read the fastest newer SD cards. You never know until you match up the card and the Garmin and try it.
(That last statement is not a made-up fact. I contacted Garmin to complain, and was was politely informed that my Garmin was built before Type 10 cards were invented, and the machine would NEVER read one ... Next question: "When is a LIFETIME MAP Subscription NOT a LIFETIME MAP Subscription???? I needed the card because later maps were BIGGER than the internal memory of the Garmin. )