There is an issue report page in the Wiki, report this stuff there if you want attention to the details you discovered.
http://www.vems.hu/wiki/index.php?page=IssueReports%2FVemsTuneThe new communication model used has changed the way information is sent and synchronized. You'll notice that you get a higher update speed, it takes shorter time to sync with the ECU and as far as I know all data transfers are now checksummed. 115200 baud communication actually works, 100+ Hz update speed on a recent model laptop. I wouldn't update the firmware at that speed though..
What you'll notice as well is that you can do offline changes and when you reconnect to the ECU it will ask if you want to send your changes to the ECU, save it to a file or discard your changes and read the current configuration from the ECU. This should've been there from day one with VemsTune, but now here it is.
As far as recommended communication settings, I use the settings that it comes with by default, and it has worked just fine with both my stationary with real serial port and the Prolific adapter used with my laptop. Now that there are checksums on data transfers the error rate will probably determine what is a good setting, don't worry about it - that will stabilise.