How much more difficult is it going to be to dig up the stump & roots of a tree that has been cut down to 1 inch above the ground ?
Difficult? Really not sure how to answer that. Time consuming and a pain in the ***? Yes. Years ago i did that with a dozen or so stumps, should have just rented/payed someone with a stump grinder to do it. But i was young, stupid, and had a strong back. Thing is with the grinding, over the years you'll need to fill the area a bit as the roots rot out and such. Not really an issue.
You hire a tree stump grinder which will reduce the stump below ground level in about 10 minutes.
Hire a local person with a stump grinder. They will make quick work of removing the stump to as much as 10 inches below the ground. Not that expensive and will save you lots of time an effort.
depending on the size tree, that could be very labor intensive. it would be easier and faster to just rent a stump grinder or hire someone with a stump grinder.
Much more because all you can do is dig. You have no leverage. The trick to getting out a stump is to leave a good piece of trunk to lever over.
When you cut the stump off at the ground, there is no way to push it over. Unless you have big equipment (bulldozer) than can cut the ground.