Typically, cast gives a little more velocity and a little less pressure.
The load into which you are subbing cast has to be one that gives velocities acceptable to cast bullets though. It's just barely possible that you could run into a light load using a very slow powder that would work with jacketed but give bloopers with cast. H110/WW296 is about the only powder with which I would worry about that.
Yes and no. Yes one can physically do it, and generally the pressure will run a little **higher** (the lead bullet seals better, hence less gas escapes, hence higher pressures [take a look at a Lyman manual with pressure data for both lead and jacketed])... but the lead bullet will generate significantly more velocity. [in a 3030ai, 9gr of unique will drive a 170gr lead bullet at 1340fps, a 170gr psp takes 12.7gr's to get the same velocity - there's that much difference in friction (and please do not repeat this experiement - the chances of lodging a bullet in the barrel are much too high)].
W/re NO - un-gaschecked lead bullets don't like pressures above 20,000cup (+/-) and will keyhole badly if driven harder than that (and will lead the barrel equally badly, if not worse). Gaschecked bullets will take more pressure, but still don't like the 60kpsi that most modern hunting cartridges will generate.
Bottom line: loading for lead or loading for jacketed take different loads with different powders.