If you go into more detail on the DfT website, Corby services are going to be worked by refurbished EMUs formed of 20m long vehicles - there is reference to 12-car trains in the peak.
I can't find any references to bi-modes.
However, St Pancras - Sheffield/Nottingham services will be worked by new 125mph trains, and there will continue to be some extensions north to Leeds and York at week-ends (no mention of Scarborough on smmer Saturdays in what I've seen so far); there will also be one service each day worked by these between London and Melton Mowbray via Corby, and two services per day between St Pancras and Lincoln. The new trains will be introduced from 2022.
Regional services will be worked by refurbished MODERN trains; all train descriptions seem to be the same, showing air conditioning, free wifi, more luggage space, and tables at all seats, etc. So its bye-bye 153s and 156s, but not sure what's meant by modern; could some Meridian's be kept for Norwich - Derby, thereby capitalising upon their 125mph capability on the ECML between Peterborough and Grantham (see next paragraph)?
Quite a few route changes, the major one being the splitting of the Norwich - Liverpool service; north of Nottingham will be transferred to another TOC early if the franchise, and the southern portion will then be extended west of Nottingham to Derby. Presume the TOC is TPE, so 185s? The Crewe - Derby service is being extended east to Nottingham, this giving three East Midlands services on the Derby - Nottingham axis each hour.