@Cali2 

I'll try to answer your questions:

>1. Will I encounter any problems with my mesh if I combine Wifi 6 and Wifi 5 Deco models

Most likely not. Some WiFi 6 capable device might not want to roam from WiFi 6 node to WiFi 5 node until signal from WiFi 6 node gets extremely weak, but this is mobile device (smartphone, tablet) specific. If you insist on having the mix of WiFi 6 and WiFi 5 nodes, this is minor inconvenience you may have to live with, or you might not see it at all.

Nothing else comes to mind.

As far as Deco mesh concerned, all units from models you listed will work together just fine.

>2. As I need to buy a specific hardware version of the product in order to have Homecare (for X60 I see that V1 supports Homecare), how do I recognize this when shopping for a new unit?

I would not trust anything stated online, even major online retailer like Amazon could post outdated info or not mention hardware version at all. For M5 and M9 Plus I have, hardware version is listed at the bottom of device. Just check your M5: it is on the bottom label after serial number. That same info is on the box M5 came with. Same for M9 Plus. I am assuming every other Deco model uses same labeling. Which means, when buying it in person at the store you can check the version on the box.

After the fact, you'll find it in Main Deco Web interface, where you can log in with the browser, using Main Deco IP address. In case Deco unit was mislabeled, you'll see actual hardware version there. Of course, Deco app will provide different features for Homecare vs Homeshield, thus giving a clue what your Main Deco has.

It appears Homecare is on its way out, so it makes sense to find the place where you can inspect Deco box (Deco unit itself) in person before buying it.