Lets see if can answer some questions for you..
Most of the emulators like c64, Amiga etc have a built in virtual keyboard you can bring up with a specific button, Dosbox does not currently have one but im sure it will eventually. Still with Dosbox you can map buttons and button combos for key presses.
In Dos box I have tried games like Ultima 6, Martian Dreams, Ultima Underworld 1 and 2, Mean Streets etc and all of those were playable with sound and the stock config.
If you like games like Secret of Monkey Island 1-3 , Day of the Tentacle and other SCUMM games your in luck, Using SCUMMVM they play perfectly and fast. It supports keyboard and mouse as well.
Hope that answered some questions..