I haven’t tried a plug too much but my wife has done a finger during a blowjob which I enjoyed. It amplifies the pleasure of the blowjob. I don’t really enjoy it on its own. I find stimulation of the perineum and base of the cock is similarly enjoyable.

Also I don’t enjoy in and out sensation too much. It feels like I’m pooping. Just the pressure of it being in.

It is also not an every-time thing for me.