bit late but is your shifting indexed. It most likely is an indexed shifting. In which case, going from 9 or 10 speed clusters to 11 speed cluster will cause problem with the indexing. So you will need new indexed shifter. If you are not using a brifter (brake-shifter combo) then the price isn't too bad. Otherwise, figure on the added cost to get a new brifter.

The other issue is with 11 speed cluster, your chain has to be narrower than 9 or 10 speed (I think there is a difference. I know there was a difference for 7/8 speed clusters). Narrower chains will wear out faster and need replacing more often.

As for ease of riding, it depends on the gears in your cluster. On flat road, I had what is known as a corn cob there was only one teeth difference between gears. 11-12-13-14-15-16 kind of thing. On events with lots of climb, I would swap out with something like 12-13-14-16-19-21 kind of cluster.

Or you can get something bit more reasonable with gearing from 12-13-14-16-18-21-24-27 kind of thing. I'm just pulling numbers here so not sure what is available these days. So don't quote me on the gearing in the cluster. But I hope this will give you some idea.