Can 192.168.1.200 resolve only .local.mesh or everything? If it would be everything, you can do simple test by setting 192.168.1.200 as the only DNS resolver for your PC. Even if it could do only local.mesh, you can still try it, to see if it makes any diffence for accessing servers under local.mesh. Only in this case, you’d lose access to everything else while doing the test.
A misconfigured DNS server can really be a problem. It’s difficult to say what’s wrong without diagnosing it on site, though.
There is a simple test you can perform.
What happens if you configure your computer to use just a valid, public DNS server (8.8.8.8, or 9.9.9.9)? (I am not mentioning 1.1.1.1 for now because it’s known to be unreachable from many ISPs.
If it works better then it’s a DNS problem.
And regarding configuration, the right way to do it if you want access to your mesh.local domains and the public Internet you really need a properly configured DNS server of your own. A Raspberry will do fine, you don’t need a lot of performance. Just the right configuration! 
Okay, I plan on doing some more testing this weekend, because I thought at first that I could live with the speeds, but it really is bad. I was trying to add a mail server on my network over to the Mesh network, and I gave up after a while just because it was too slow to function. It takes around 20 seconds or more to open any pages past my NAT node of 192.168.1.200, so I will directly connect my node this weekend to be sure that speeds are still good if I bypass the router.
I did a little bit of testing here this weekend, we had a huge lightning storm and we think our mountain top site may have been hit, so we have spent most of our weekend rounding up part to go up and try to get it online. I did get a chance to test using only the 192.168.1.200 as the DNS for everything, and it does work, but it is no faster. I don’t know if this will shed any light on the subject or not, but when I am using my VPN connection from my office, I can access 192.168.1.200, but if I try to go past that node to anything else, I get nothing. no other pages will load. Like I said, maybe that will shed some more light on the other issue, but if not, just disregard.
I guess you may be missing route to 10.x.x.x from VPN. Or VPN client can have IP address from some other subnet and the gateway device (192.168.1.200) refuses to let it pass, or doesn’t do srcnat for it (target devices wouldn’t know where to send replies).
Anyway try running the test linked from this website:
https://www.dns-oarc.net/oarc/services/cmdns
It may shed some light on DNS server problems.