What's the application?
Depending on your usage and needs there could be better solutions.
For the SB Cruiser trike's rear wheels, I use Shinko SR714 16x2.25's (really a moped tire vs heavier MC) on some old 50mm rims (some kind of doublewall "BMX" rims that were used on the original Zero MCs), and they are no harder to put on than some bicycle tires are. (for instance, the CST Sensamo Control tire I just installed on an ancient Sunlyte Mammoth Fat 26" rim took some work to get on).
I do trim off a couple of mm of "flashing" at the inner edge of the bead of the tire, that is not involved in seating or sealing it, to make it even easier to get on and off.
Lubrication (liquid soap, for instance) can help a lot; you can use zipties to push the beads you get on first down into the well and hold them there while you work the resst of the tire on (and then you can remove those and use different zipties to force the installed tire evenly down onto the rim while you inflate it so it ends up round.
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How easy they are to install/remove depends on your specific rim, the wall/bead height vs the depth of the rim inside that, and if it has a deep well for the beads to go down into on the side diametrically opposite the one you're levering over the rim, it will be easier than if there's no well there (where the nipples go into the rim).
Rim width doesn't directly affect how easy or hard it is to get the tire on--that has to do with the design of the rim itself and that of the tire's bead and sidewall.
The width of your rim should match the width of the tire you'll use on it, within some range--if it's too narrow the tire will wobble around on it and handling will be poor. If it's too wide the tire will all sit within the rim and you could get rim damage or tire problems.
There are also at least two common sizes of "20-inch" rim, a 406mm (what I am using AFAICR), and the larger 451.
some others in the ISO list off the Sheldon Brown site (not including the "other" standards out there):
| 451 | 225.5 | 20 x 1 1/8; x 1 1/4; x 1 3/8 |
| 440 | 220 | 500 A |
| 438 | 219 | Dutch juvenile, 20 x 1 3/8 NL |
| 428 | 214 | Swedish, 20 x 2 |
| 419 | 209.5 | 20 x 1 3/4 |
| 406 | 203 | 20 x 1.5- x 2.125 |
So depending on your chosen MC tire, there might be a better fit for a rim for it...but I would guess from my own experience that the smalles of these, the 406, is probably easiest to get on and off.
For really thick MC tires they're likely to be difficult to get on and off even on a MC rim; the sidewalls just arent' flexible like thinner ones on moped or bicycle tires.
