I own both the Explorer2 and the iFi Nano BL. Overall, the iFi is the better product, especially as a reasonably powerful headphone amp and as a portable, battery-powered DAC. So I often use my iPhone as an untethered Roon endpoint driving Audeze cans.
Even though it has a more accurate sonic signature to my ears -and balanced output if you use the appropriate cable-, the iFi is just a renderer while the Explorer2 will both decode and render MQA. Hope that helps your decision.
Theater: C61R, DSP5200SEs,420s,33s, NHT amp/subs, HD621, 218, DigiOne, OPPO 203, JVC RS500, Fire,Apple,DirecTVs, Mac Pro 2010+, MF V-LINK II, REGEN and iFI conditioners
Also: 598DP, 568.2mm, 565, DSP5000.2s, Roon endpoints incl Allo USBridge, Explorer², iFi nano iDSD BL, Audeze LCD-X, AudioEngine spkrs, M&K sub, Apple MBP, OPPO BDP-83