No, stamps aren't really issued in "standard" sizes but most countries have sizes that are fairly standard for many of their stamps. But not all. One country may issue stamps in many dozes of different sizes.
Many album manufacturers sell albums with mounts already in them. They're called "hingeless" albums, and they're very expensive. They include Lighthouse, Schaubek, Davo, Stanley Gibbons, Marini, Yvert, Palo, Mystic Stamp, and even Scott which sells a Schaubek- made album with Scott National pages in it with mounts. And there are others, as well. No mount cutting problems with these albums, but you pay a big price for them. A thousand dollars for an entire country would not be unusual. That's why most collectors put their own mounts into their albums. It sort of spreads out the expense over time. I suppose the cost of an album plus the cost of the mounts is less than a hingeless album, but I've never seen anyone add up the costs to show how much less.
With lower-priced or blank albums, you have to put the mounts in yourself -- if you use mounts, that is (there are also stamp hinges). That usually involves a mount cutter, a little guillotine device, that makes cutting mounts easy and accurate. But scissors will work even if they sometimes cut a mount at an angle which doesn't look so good.
Buying mounts specifically sized for certain stamps is more expensive, but easier. Cutting them yourself is cheaper. And there are a huge number of sizes you'll need to deal with all sorts of differently-sized stamps. It can be a bit overwhelming!
Black mounts are most popular but clear mounts are easier to use since they don't show mistakes as easily. On an album page, a misaligned black mount can be really noticeable. A slightly "off" clear mount isn't noticeable. Clear mounts also let you see what's behind the stamp which may be stamp information, catalogue number, and so on. Black mounts cover that up. When combined with stamp hinges, clear mounts generally look better. An album that mixes black-backed mounts with stamp hinges always looks messy to me, but you may not see it that way.
All hingeless albums that I've seen use clear mounts. On blank pages, black mounts provide a background for each stamp which looks good, but clear mounts can look good on blank pages, too. In printed albums with thin pages, the weight of all the mounts weighs down the pages noticeably so maybe not a good idea to use them in cheaper albums. They work best on heavier pages.
Believe it or not, but some collectors still use stamp hinges! I use hinges for all my used stamps and for "mint" stamps with hinge marks on the back. I have entire albums mounted with hinges. Can I say that today? Hinges, even at the expensive prices the good old-fashioned hinges sell for today, cost 1-2 cents a hinges. Compare that to the cost of mounts which are far more expensive. And it adds up. An entire album mounted with hinges costs maybe $20-30. With mounts? Much more than that.
The key thing with hinges is not to moisten them much -- and to use, if possible, older classic hinges like Fold-O or Dennison which you can still buy on eBay
. The older hinges had a better glue that released easily when it dried, thus not damaging the stamp at all. More modern hinges have more aggressive glue on them. They need more care in not getting them too wet. A good approach is to moisten them only very lightly, then wait at least a few seconds for the moisture to evaporate, then apply them. Never apply a really wet hinge to the back of a stamp or you may never get it off again.
MNH stamps should probably go in mounts, however, but frankly most modern MNH stamps are so very common I don't quite see why that's necessary most of the time. There are differences of opinion on this, of course, and we don't want to ruin a stamp just because we're cheap, but I see a lot of used common stamps put into mounts and I wonder why? I suppose it protects them, but isn't that the job of the album and the interleaving? Mounts also add bulk (thickness) to your album. An entire album filled with mounts will bulge due to the thickness of the stamps plus the mounts. You may have to remove some pages and put them in a second binder to deal with that. HInges vs. mounts isn't a simple good or bad propostiion.
Various kinds of mounts, clear and black, split-back and three sides open are available at all the usual websites -- Amos Advantage, Subway Stamp Shop, Potomac Supplies, etc.
As for glue sticks, they can be bought at office supply stores (and other stores) or on Amazon
. In fact, some stamp mounts may be sold on Amazon
). Browse around. All of this stuff is widely available.
Anyway, that's everything I know about mounts -- and hinges. Enjoy!