12, 16, 20, 28 gauge, or .410 bore, depending on what it is chambered for.
Depends on what it is choked.
Yes.
The Express version of the 870 Remington is normally either 12 or 20 gauge. Gauge desigantion is marked on the barrels left, rear end.
Each weapon will exhibit a preference for a certain maker/load combination. The only way to know is to shoot as many different loads as you can find.
About $325-$350
the express is the cheaper model Remington came out with. There are many more models like the tactical ones and the wingmaster. The wingmaster is one of the better quality models.
The 870 Wingmaster is still made in .410
100-375 USD
Around $350 depending condition.
There are many places one might go to find a review for the Remington 870 Express. The most reputable resource one has is the Consumer Reports website.
Is it a Wingmaster or an Express? Can't be both.
No requirement that it has to be.