I do a combination of the above. I add pages and (gasp) have been known to put a stamp in a margin, mount a copy underneath if I have 2 copies I want to keep (usually cancellation related) or even to add missing stamps to the set. Honestly, I don't care if it's a little messy looking.It's my album and I'm having fun with it. I also have Scott Specialty Albums for countries that I want to get more in depth collecting and those I am pickier about appearance. It's your collection. There is no right answer. Do what makes you happy.
I bought the reprinted Scott International pages. They are thicker paper and each country starts on it's own page. I then bought Lighthouse binders and Vario stock pages. I put the pages in the binders and added the stock pages, one per album page. I put ALL stamps into the stock pages, matching the positioning of the album illustration/space as closely as I can. For the stamps I acquire which don't have a spot on the album page, I simply add them to the stock page. This way I can keep a "cheap" stamp that Scott left out. I don't go after the more expensive exclusions. More shelf space, that's for sure. Did I mention I hate using hinges?