I have a TG-6 and I have used YS-01, DS-51, and Backscatter MF-1 strobes.
For TTL use, the DS-51/RC-1 has always provided better results for me than the YS-01 in TTL mode. With the RC-1/DS-51 combination, you set the TG-6 flash mode to “RC” mode. Do you need TTL shooting? Not really, but I like multiple tools in my tool belt and there are cases where TTL can be quicker than manual strobe settings…some times you only get that one chance for the great shot.
The YS-01 results using TTL were so variable, I ended up using the strobes in manual mode. I eventually sold them. The Backscatter MF-1 only operates in manual mode.
My personal experience is “if” you see yourself using TTL, the DS-51 with RC-1 using “RC” flash mode on the TG-6 will provide great results. Backscatter has released a new strobe, the MF-2, which also supports the TG-6 “RC” mode, but I have not used that strobe. But it is something to consider.