I installed a 199,000 tankless to see how that is like.
My 15 year old gas water heater had failed, so it moved up my timeline to make the switch.
I installed the tankless near the gas meter. The existing gas line, which shared with the furnace was too small for that much flame. I had two tankless units in boxes, and I was thinking of running them together. I haven't installed the second unit yet.
It now takes quite a long time to get warm water. So long that I sometimes skip washing my hands with warm water, and just use cold. I need to either install a recirc line, or move the tankless near the bathrooms.
Navien makes a nice tankless unit with recirc and buffer tank built in. In Northern climates, the 199,000 puts out about 5.0 gallons a minute. It may do a lot more in Florida, but I don't live there.
I also use a tankless at Sue's. That tankless in in a corner between the two bathrooms. There is plenty of water for two showers at once, and since we're only talking a few feet, there is no time lag.
One more reason I'm thinking of moving the gas line in my home and putting the tankless in the same location as my three bathrooms, which all share common walls.
Many gas meters will handle a 80,000 and a 199,000 load, but your gas company will have records and be able to tell you.
The longer a gas line is run, the larger the pipe needs to be. CSST needs to be larger than hard pipe.