can MTH Real track connect to MTH scale track

Only if there was a transition piece offered which I doubt.

With difficulty.  You'll have to ballast/shim underneath the scale track to get the rail heads level and devise a means to keep the rails in alignment.  Other than solder, there are no transition fittings to connect the rails together.

I have read recommendations to grind a tubular pin form factor in the ends of scale track rails and plug into tubular (or a RealTrack transition section).  After building turntables and lift gates, I feel keeping alignment of unjoined track is simpler than grinding.

I dont see it going well. Everything from the height of the track to the height and profile of the rails is going  different. Can it be done? Probably, but you're likely going to need to but them up, align the tops of the rails and then solder the daylight out of it, then sit there with a file and work the transition down to something smooth enough to not catch a wheel or pickup roller.