According to that, it went as a B752 yesterday (the 19th), so it's using that data to predict what equipment the next trip will use.
The Q suffix designates that the flight is using RNP and RVSM. Sometimes they use different systems, which are denoted by different suffixes (you see lots of different suffixes on FlightAware).
What you'd be interested to know is that your aircraft tomorrow for flight 1297 will is categorized by DL
as a 73H, not a 738. The H means that it's an -800 with winglets. For Delta, that also means you have Wi-Fi, PTVs with AVOD and satellite television, and USB power ports.
Just checked delta.com
and your second flight is on a standard 738. There should be Wi-Fi while you're still over the continental USA, but there will be overhead screens for other entertainment. Also, the flight on the 19th was indeed a B752 (must've been a sub). Today's flight was on an 738 (not a 73H). Looks like you got lucky.
As for the registrations (I can't believe I just did all this), DAL535
will be N3740C
. I wasn't able to find DAL1297
but it might be N3766
based on the departure times although gate numbers don't match up so I wouldn't count on it.
Tho' I've belted you an' flayed you, By the livin' Gawd that made you, You're a better man than I am, Gunga Din!