I just tried both.
I had no problem with MNST irrespective of primary exch (none, ISLAND, NASDAQ). I typically prefer ISLAND since this is what the documentations seems to suggest for outgoing requests (not sure this is up to date, but it doesn't cause problems).
I had weird problems with TCEHY initially, with the API complaining I have no subscription for?ARCAEDGE data for some reason, which doesn't look right and indeed all real time and historical data are available for me in TWS for this stock. However after a few attempts with no intentional changes to TWS or obvious side effects, these problem are now gone for me and I can receive historical bars through API with ANY primaryExch including none, PINK (which is its primary exch per contract details) and even SMART, ARCAEDGE or OTCLNKECN. I can't reproduce what I did exactly to bring it back to its senses but one of key things seems to be requesting contract details, though I didn't use them for getting historical data.
