The developer actually has this settled. If you read that post above, it’s kinda convoluted but that’s due to Garmin and their restrictions.
There’s no need for Dual Recording indoors anymore. Anyways, there’s no downside to doing dual recording if you still want to with that feature. But in Garmin Connect, ur Fenix will not have data like speed/distance (if it matters to you - u said u like badges, I’m unsure how that works cos no distance = No dist badges).
BreakAway will upload to intervals.icu & Strava. But u will get duplicates from Garmin (from Fenix) as that data has no distance etc so I suspect intervals.icu duplicate detection might not work as great.
Right now, I’ve stopped dual recording, uploads direct to Strava/Intervals/Garmin and no duplicates thus far. Also get my VO2Max (I think) and Training Load updated. (But… TSS/Load numbers will vary between sites, I usually don’t worry about it that much as diff sites may use diff ways of calc NP. )
I believe TD has something similar but is using another 3rd Party App (RunGap - need subs) to do the syncing.