UPDATE - As Status Quo once famously asked “Is There A Better Way ?”
OK this may be of interest to some users but after a week, of snap crackle and pop, playing in a cavern and then finding one of my webcam mics was picking up my vox and guitar and muddying video recordings in Zoom, I have found a more elegant way of connecting Reaper to OBS. So Yes that was the issue at OM5 not my studio mic after all 
This does not involve Reastream and therefore does not piggy back audio via the backdoor using an unused Webcam mic to capture audio ! This is a direct route from Reaper to OBS.
Using ReaRoute and works a treat.
This guy explains it far better than I ever could but it follows on from @Majik Keith’s piece on using OBS-ASIO but this time its connecting Reaper and OBS. Connectivity from OBS to Zoom remains the same.
So two weeks after getting a good Open Mic set up recorded in OBS via Reaper and subsequently finding it all went pear shaped when it got to Zoom, at 22:45 yesterday evening I finally fixed the issues, with this method. Yehhaaa !! 
The only down side is not being able to record Zoom in OBS. Not something I planned to do but possible using a pair of virtual cables to route audio and video back and forth between OBS and Zoom. Using this method and both cables resulted in a huge satellite delay, making my “set” unplayable. Reverting to the single virtual cable, described in my original guide resolved that issue and I was able to record in both Reaper and Zoom simultaneously and by midnight was a much happier bunny. 
I hasten to add, this is an advanced method delivering audio and video to Zoom and is NOT mandatory for our Open Mic set ups, which should be done following this guide
The method described in the guide here, allows you to effectively mix and master your audio in readiness for a “show” and is just a tad more complicated than propping your mobile on the table in front of you. That works just as well and you sleep better.
As usual any questions, I’ll do my best to answer.
Cheers
Toby (anything for a quiet life) The Madman !
