which village on Lake Como

The Como towns most often mentioned here are Varenna (smaller) and Bellagio. They both are distinctly hilly, and I don't know how readily available taxis are; there's a lot of money in Bellagio, so I imagine it has more taxis than Varenna. (Others will be able to comment on that, I assume.) Menaggio, which is also on the very handy mid-lake ferry route, is noticeably flatter. I found it very attractive but will concede that many would consider Varenna and Bellagio somewhat more picturesque. The problem is that they are more picturesque partly because of their hilly, squirrely streets.

One thing visitors to Lake Como enjoy is visiting the fancy villas and their gardens. The villas are typically set up on a hill; it would be important to figure out what sort of allowances are made for people with mobility challenges to approach them.

I haven't been to Lake Maggiore or Lake Garda recently enough to make comparisons to Lake Como.

Menaggio on Lake Come is far less crowded than tiny Varenna. which can get completely overrun with crowds delivered regularly by trains arriving all day at its train station. Menaggio is also far less crowded than Bellagio— whose fame has become a double-edged sword as it seems to be the one Lake Como town that everyone visits. In season, It can be difficult to move through the throngs of visitors on the streets of Bellagio. Mennagio has the added advantages of being relatively flat, which makes visiting it easier—and scenic because it faces the other two towns which are on the eastern shoreline of Lake Como.
Menaggio has taxis , actually has a couple Agriturismos you can stay just outside of town, and is just a 15-minute ferry ride from Bellagio and Varenna.

Both Garda and Maggiore are flatter with more room to spread out/ avoid crowds

Where are you going after this stop?

I would say that only Menaggio is suited for people with disabilities. Varenna and Bellagio are hilly and with plenty of stairs and steep alleys.

I like Varenna and we stayed there before covid, and before my wife got her white cane and rollator (4 wheeled walker). At that point we had no issues with the walk along the main road or the lower one, or joining both with some of the lanes, or getting to and onto the different ferries at the dock.

Granted that everything is up from the water, but I would say that the main road is nearly the highest bit, the church a little higher and the multi-storey car park a little higher still, but my memory is that the main road from the water is maybe 2 or 2 and a half stories to at most 3 stories. Depending on your wife's mobility issues she may be ok with that. I am confident that mine could if I was guiding her and we stopped halfway. The only problem with the rollator is that because the white cane mounts to the side and only the top is visible motorists and pedestrians don't recognise it for what it is and often don't give her the room she needs - that's why I guide her.

If there is anything else I can do to aid with access issues I'm happy to help.