No disappointment here - it’s good to hear that things are coming together for you and you are getting to appreciate the massive difference IEMs make and why all bands should be heading in that direction.
As far as your choice of IEMs, the key thing is that dynamic in the low. That should give you that all important headroom that a single balanced armature can’t do very well. The harsh/loudness is probably down to the tuning of the IEM and the fact that it’s not got a driver dedicated to the midrange. The BA may be a compromise between the highs and the mids or dedicated to the mids and not so good at delivering smooth highs. In reality, I don’t know - I’m just guessing... but the key thing is, you've got something that is closer to what you need out of the box and gives you a closer starting point to fine tune with the aux EQ.
This is all good reading though - and as you say, when you factor the cost of what a monitor is and what you could achieve in ease of transport and quality of monitoring, it all starts to make total sense.