Background: I'm a married 30-something who's been a nomad for 3.5 years. The first 2 years I worked remotely for a US company and stayed almost exclusively in the US. I quit my job 1.5 years ago and we've traveled almost exclusively abroad since. I'll take your questions one by one:
is it everything you thought it would be? Yes. Not saying it's a magic bullet, but it's pretty awesome
Are you enjoying it or do you have regrets? None. When we started this, I was expecting it to last a year or maybe 2. 3.5 years in, I'm not 100% sure we'll do this forever, but for the foreseeable future.
Is it more of a hassle than you imagined it would be? My wife loooves booking flights and places to stay. Some things are hassles, but you pretty quickly learn to avoid those things and do the things that are worthwhile for you.
Do you feel somewhat adrift and disconnected? Homesick or missing interaction with family and friends? Sometimes. I do miss random interactions with people on a regular basis. OTH, I have had far more meaningful interactions with friends and family these last few years. Instead of lunch when they're in town a few times a year, I can stay with a friend for an extended period. You have to be sensitive and know what works for that specific person, but it can be truly wonderful to get to be part of someone's life for a little while. That said, I think I'd feel differently if I were single. My wife provides most of the human interaction I need
Expenses higher or lower than planned for? When we were in the US, it was higher, but I had a job which A. made it necessary to stay more reliable places and B. made me less budget conscious. That said, the US lacks many of the budget options that you find abroad. Abroad: quite a bit cheaper than planned. AirBnB is remarkably cheap in most of Europe/SA. Hotels are so cheap in Asia. Not having any fixed expenses makes everything so much more reasonable though. Yes, there are times when you'll be paying more than you want, but there's also times you'll be somewhere very, very cheap for an extended period, with no mortgage/rent/anything on top of that. I once spent $200 in a month.
Do you wish you had done it differently - maybe a different mode of travel or longer or shorter stays in one area at a time? We started out quite cautious, staying each place quite a while. We eventually moved to much more active travel for a while, and have now slowly moved back to slower and slower travel. Sometimes traveling actively is fun, sometimes it's exhausting. The more you do it, the more you know what you'll need and find the right balance for yourself.
If you've tried different modes of travel/living or locations which did you like best/least? I love camping, but can only do a total of maybe 2 months a year. I love SE Asia, but get a bit sick of it after a few months. I haven't found a perfect place that has everything I want and no annoyances. Combining everything I've managed to find a pace and a variety that works for me, but your mix will obviously be different.
If you had kids or pets or are single and going alone how much harder or easier did that make things? I think the dog will be a huge issue. For me this life only works because of the variety of things, places, styles of travel I can do. A pet will severely restrict you geographically and in terms of what kind of lodging you can use. To the extent that it restricts you to the US it will cut out a lot of cheap nice options.
What is your backup plan in case you got seriously sick or injured or just decided you were done? Go somewhere and get an apartment. It's not that difficult.
Did you decide to call it quits earlier than planned and went back to buying or renting in a fixed location to stay permanently? Not yet.
My three biggest pieces of advice:
1. if you're single, really think about how you'll get whatever amount of social interaction you'll need. We're all different on this front, so this may be a huge issue for you, it may be nothing. I've traveled alone a ton, but I'm 100% sure I wouldn't be a nomad still if I were doing it alone.
2. Think about how/where you'll spend your down time. My guess is I spend 6 months a year just relaxing various places. If I wasn't able to spend those 6 months extremely cheaply, I wouldn't be able to live this life on my budget.
3. It sounds like you've already sold your house, unless I'm missing something, it doesn't sound like it'd cost you anything to go down the path of being a nomad for a while and seeing if you can make it worthwhile for you.
Good luck and let us know what you decide and how it goes!