Brompton BWR Hubs are 28 spoke hubshells, 117 wide OLD, so 120 wide frame dropouts..
in NY the Brompton dealer,
https://www.nycewheels.com/brompton-folding-bike.html
BWR is .64/1/1.57 , the AW3 & BSR are .75/1/1.33.. I have no idea if the drivers can be swapped...
Todd the owner of the Portland Oregon Brompton dealership, Clever Cycles, would know about the Titanium 3 cog cluster,
since he wrote about touring Eastern Oregon using one..