I can't comment on the model Garmins you are talking about, I use a Garmin 64. I want a GPS that runs on AA batteries and is good for general recreation like canoeing and kayaking, in addition to cycling.
But I assume you can load maps from the internet onto some of the Garmins you are discussing. Not sure what areas you are interested in (N Amer, Europe, etc.). Some of the sites I use to obtain maps are:
https://extract.bbbike.org/
At the above link I use the Openfiets Lite UTF 8
USA OSM Topo Routable | GMapTool
https://www.openmapchest.org/
I think these are non-routable, but I use them for canoe and kayak trips.
https://www.gpsfiledepot.com/maps/byuser/135/
I use Mapsource (a no longer supported Garmin program) on my computer, some of the above links I load the maps into my computer, then into Mapsource to transfer to my Garmin. But other above links give me the file that I need to directly transfer to the Garmin.
The go-to site that I mostly have used became dysfunctional a few months ago, so I did not list it here. But since I used to mostly use that site, I do not recall a lot about how I used the other above sites. Some of these links I have not used for a few years, but I assume they still work ok. I am not a great wiz on this stuff, I am sure there are others on this forum that can explain this better than me.
ADDENDUM ADDED LATER:
When it comes to planning routes, not only do I use my Garmin 64, but on my Andoid phone I also use the apps Maps.me and Komoots. Map.me can be used off line for routing, Komoots has to be on line.
I recently finished a five week tour and most days I deviated from the routing that I got from the Garmin and the other two apps because sometimes the devices were trying to take me off of bike trails or they were trying to avoid a perfectly good road.
My Garmin 64, for routing I usually use the Cycle Tour option and the Minimize Ascent option. But sometimes I check to see how the car driving option compares to the bike option.