It’s hard to evaluate these impressions without knowing what length stems people are using, as that has just as much effect on steering/handling as the length of the fork.
If you go from a 100 to a 120 and leave everything else the same, you are bound to slow the handling down. Although people often insist it makes no difference, this is just wishful thinking or that they like the increase in travel so much that the handling still feels fine to them. However, you can keep about the same kind of handling as you had before if you combine the longer fork with fitting a 15mm shorter stem.
Obviously if the bike already feels a bit small, you don’t want to make it even smaller, but if the bike currently feels slightly on the long side then fitting a shorter stem and a longer fork is usually a pretty good plan.