The reason I am asking this question is I have pre-ordered a "Switch e-bike Conversion Kit for my new Huffy Rock Creek Mountain Bike that has 29 inch tires. The Swytch system will ship with a replacement 29 inch tire including a front hub mounted motor. If I want to later mount this same Swytch kit on my Giant Sedona that has 26 inch tires at present is there enough space on the Giant Sedona to accomodate the larger 29 inch tire size?
You cannot just mount a larger tyre, even if you had the clearance. The larger tyres need also need larger rims, that usually means you need complete new wheels.
It is unlikely that a frame for a 26er would have clearance for 29 inch wheels and tyres even if you bought them. Unless it is a 29er Giant Sedona just used with 26 inch wheels, but I consider that unlikely.
If they are disk wheels, it may be remotely possible. If not, no, the rim brakes in the wrong location. 29" is much larger than 26". Being the front fork, its possible, but unlikely a 29er will fit (Unless the fork is for a 29er).
You could try putting the existing 29" Huffy wheel on the Sedona . If it fits, then you would likely be good to go with the new wheel (however width of the new wheel and tire might be bigger is its not certain).
If this does not work, you can potentially change the fork to a 29" and "Mullet" the bike (29 front, 26 rear), but the bigger front wheel changes geometry and affects the bikes handling (could be good, bad or indifferent - details require another question), and a fork swap on a MTB is expensive.
If I want to later mount this same Swytch kit on my Giant Sedona that has 26 inch tires at present is there enough space on the Giant Sedona to accomodate the larger 29 inch tire size?
Almost certainly not.
The cheapest way to adapt an ebike kit to a 26 inch bike would be to take off the spokes and 29 in rim and rebuild the front wheel with a 26 inch rim and spokes. Though considering the low pricepoint of Swytch kits, it may make sense just to buy another one for the another bike.
I cannot comment on the resulting dynamics and riding quality of such a bicycle, but yes you can (however I feel the question is "if I can, should I?")
You can change the fork on your bike, creating a so called "29/26 frankenbike". With the right fork, the geometry will somehow work, avoiding issues like footstrike on the wheel or (too) awkward riding positions.
In fact, such a set up was considered to be a viable option, there was actually at least one commercial sold bike with this set-up, the Trek 69er. However, there are plenty of exotic commercially sold bikes that looked like a good idea, but they weren't.