An answer to a previous question of mine suggested gluing two boards bark-side to bark-side in order to compensate for possible cupping. I'll likely be buying the boards at a big-box store (Lowes) and am wondering if the boards are really suitable for gluing as purchased? Are the edges flat and true and square enough, or should I do some cutting beforehand? I have a table saw and router (with table), and have seen some interesting jigs on youtube to square up faces and such, but would prefer to avoid the extra work if I can.
As with many answers, it depends. You should check all the boards with an accurate straight edge. You might be in luck and they are still flat enough to glue, in which case go for it. Or they might have bowed, cupped or warped in which cases you will need to joint/plane them to get them flat enough to join.
And of course, sorting through the wood at the big box store is always worth your time to ensure you get the best lumber you can.
One thing to note however is that some of the SPF lumber you get at the big box stores will have the edges rounded ever so slightly. If this is the case, and you glue them together, the resulting surface will not be perfectly flat. You can rip 1/8-1/4" off each side to get rid of the round-over.
and am wondering if the boards are really suitable for gluing as purchased?
Different woodworkers would answer this yes and no. Note that this is if they were looking at the exact same boards :-)
Regardless of individual standards for 'good enough' you should prep the wood prior to glueing it up because ideally this should be done using freshly worked wood. See also, What do I need to do to prepare wood for gluing?
Are the edges flat and true and square enough, or should I do some cutting beforehand?
Because of the way wood like this is machined, with rounded edges, you will have to rip off some wood to end up with square sections when you're done. This can be done ahead of time or after the glue-up as you prefer.
I have a table saw and router (with table), and have seen some interesting jigs on youtube to square up faces and such, but would prefer to avoid the extra work if I can.
Squaring the faces of boards is a job for some kind of plane or a wide-belt sander, not a table saw or router.
Anyway, in short sections it's very likely the wood will be flat enough for you to work with since you're unlikely to buy any pieces with a bad warp or cup to begin with
I would just make sure they're reasonably flat (flat enough that they'll come together using just hand pressure, or light clamp pressure), lightly sand the glue faces to clean the wood, then glue and clamp.