These are not the 3 viable options for rapid transit along Sheppard, interlining is not necessary or even desirable.
In Option 1, there is no need to interline the Sheppard line with the Spadina line. You can run Sheppard to Downsview Park and further to the Bolton Line at a minimum. This would be a true Northern Crosstown, because it'd be so much faster with the wider station spacing and grade separation. You can even elevate it after Sheppard West using some of the space there or use the bridge over the Earl Bales to transition from underground to elevated.
And an elevated line along Sheppard is doable even with the existing rolling stock and could reach Malvern Town Center travelling the south side of the CP ROW, you could transition from underground to elevated between Pharmacy and Warden
I personally don't think that there is any need for an LRT along Sheppard East, if we commit to elevated a metro line down the median of Sheppard. The additional expense of building an elevated guideway is worth the benefits of grade separation and increased travel speed.
This would be a true crosstown North. No need for changing platform heights, linear transfers, changing technologies etc. It would connect with 4 GO lines, 4 Metro Lines, with potential cheap westward extensions over the Humber.
Light purple being elevated, dark purple is underground