Joe,
In a marine environment I'd suggest using a laptop computer. Perhaps even a rugged laptop of some sort. Any laptop that has a mid-range i5 processor in it or faster (or equivalent AMD CPU) will do fine. I'd buy the largest laptop you think you can fit on the chart table
because having more screen real estate is helpful. You don't need a lot of memory, 8 or 16GB is fine. You don't need a lot of disk space, but a solid state disk (SSD) is not only faster, but far more rugged for the marine environment. Finally, you do want it to be running Windows 10, as the most capable software for the radio is PowerSDR (soon to be replaced by a version called Thetis), and that is all Windows software. Also ensure the laptop has a GigE Ethernet port. The radios only run at 100MBit/s right now, but in the not so distant future they will run at gigabit network speeds.
The differences between a 200D and a 7000 are minimal. The receiver and transmitter performance is slightly better on the 7000, and the 7000 has a nicer set of connectors on the back. Since these are
software defined radios, all of the cool stuff is in the
software, and since both radios
use the same software, they both have all of the same features, e.g. NR2 is the same on both radios. The hardware only does preselection filtering, signal routing, up and downconversion, and amplification. EVERYTHING else is done in the software.
If you are not knowledgeable about Windows this is going to be a VERY steep learning curve for you. Windows or Linux based SDRs are not anywhere near as simple as knobified SDRs (like a 7300 or 7610), and both Windows and Linux need care and feeding by themselves. Not saying not to get a radio, but fair warning if you are not a Windows jockey
73!
Scott
P.S. Since this topic does not really fit well into the other various sub-forums, I moved it to the "Everything Else" sub-forum.