Would encourage you to go to Mobile Internet Resource Center & review their information since it appears you are a 'newbie' to being a nomad & depending on internet. The information there should provide a basis on what is available based on your needs.
You mention working from parks..... there are all sorts of RV parks, private, city, county, state, national & what have you. The general consensus is the WIFI service they supply is not the best.
There are exceptions.
I have worked from my home since 2007. My wife & I became full timers in December 2019. Reliable internet was essential for us. I decided to go with a commercial grade cellular modem with the flexibility to use multiple carriers (not necessarily concurrently) as well as the ability to capture free WIFI (when available). At the time, it appeared products from Cradlepoint & Peplink were the most widely used (in this category) by us nomads. Of the two, I chose a Peplink product & have no regrets.
I suspect you biggest issue will be acquiring data plan(s) to allow you to effectively use you equipment. At the time of my research, the consensus opinion seemed to indicate Verizon had better coverage nationwide, but, AT&T was considered faster. I was already a Verizon cellular phone customer & was not interested in changing providers. I looked at what was available from them. I also acquired a grandfathered AT&T data plan (now limited to 500GB/mos) from a reseller (proceed with caution here) that has worked out very well, and, I use it as my primary connection. Redundancy of internet sources is essential, as no carrier will meet all your coverage requirements.
As a general rule, I do not stream media (TV, Prime, Netflix, etc., etc.) over my cellular connection. We are fortunate to have decent park WIFI where we are sheltering in place.
As our RV shell is not metal, I have yet to install an outside antennae. To date, the paddle antennas which came with the Peplink product have worked very well.
As I do consulting work, my workload varies. I consume between 100GB - 200GB of data per billing cycle. I would encourage you to determine, as best you can, what your data requirements will be. How many PC's on line concurrently, what apps are running that require bandwidth, is it constant use, intermittent use, can it be scheduled to run at night & so on.
What ever you get...... make sure your cellular provider supports the product prior to making a purchase.. I think the term they use is 'CERTIFIED'. I'm sure many of the suppliers will tell you the equipment will work wit so & so provider. There is a difference between 'it will work' & being certified by the carrier. The Peplink forum is a good place to browse to get an idea some of the issues users encounter & solve when the product has not yet been certified.
What you are considering can be done satisfactorily if you have reasonable expectations & plan your trips to ensure you have adequate cellular coverage.
Good luck & safe travels.
