I'll give this a try.
1) Is the 19G too small? 21ft is the max the side of my driveway can handle without encroaching on the sidewalk. Am I wasting my time?
Each of us will have our own needs regarding size. 21 is a bit tight at least for me. At about day 10 on the road the walls start closing in with my 30' coach.
2) is Thor a reputable brand? I used to be a mechanic a few decades ago, so while I can fix things, Iíd rather drive it. I do realize Iím posting this a Thor sub-forum, so the answers may be biased.
If you read enough and get past the bias ownership brings (good and bad) there is no perfect or even near perfect chassis or house builder. My Ford/Thor rig hasn't been problem free but we've never had to come home early or been left stranded for any problem.
3) I read nightmare stories about Good Sam service plans. What else is there available? I understand Cruise America has their own warranty as well
Again there will be a bias with any service plan. I avoid them while there are owners that won't leave the driveway without. You'll need to read the fine print regarding what is and isn't covered. What you should look for is emergency roadside assistance. This is towing, tire changing and such. Usually about $100 to $200 a year. Use it once and it pays for itself. Stick with providers that specialize in RVs rather than something like a once size fits all.
4) Anybody else buy a 19G from Cruise America? How was your experience?
No experience with either.
5) For some reason the models in CA donít have an awning. Is it difficult to add one?
Not unusual for a rental to not have an awning. Leave it extended in heavy weather and you can damage it. Remember renter usually have little experience and might not remember to bring the awning in when the weather starts to turn. Yes, easy to retrofit but there are alternative such as an Easy Up for a tenth of the cost.
6) Is there an equivalent of Tesla Autopilot?
Not at this time. At best basic cruise control to maintain speed.
7) Is there am EV motor home platform available?
Not at this time.
8) I can buy the motor home with cash, but I understand there are certain tax benefits of there is a loan on it? Admittedly I have not Googled this one up, but will soon.
The tax benefit is interest on the loan might be deductible as the rig might be classified as a second home. That's might, several times. You'll need to seek out professional guidance regarding if you can deduct the interest. Remember the Feds got Al Capone on taxes not all the other stuff he might have been involved in.
Good luck with your search and look beyond the dealerships for a coach. For sale by owner listings are full of good (and some not so good) rigs at lower prices than what you'll find via dealers.