devtrackers.gg
You can target cards down in the pile as well as hovering already locked in targets on the stack. It's an absolute pain in the arse, but it's possible.
UnspokenRealms is correct in that clicking any card in a pile of identical cards will reroute that click to the topmost card instead. Cards get piled together if they are identical (based on many criteria), so the result should be equivalent--in theory. If a pile has attachments and/or exiles in it, then clicks will not be rerouted.
As for the triple Fervent Champion case, a fix had been deployed months ago. So unless the behavior has regressed--which does not appear to be the case after double-checking--getting all three Champions to 2/1 is very much possible, although there will always be room for UI improvements. Remember to use the mouse to hover the Fervent Champions' triggered abilities on the stack to see what creature has been targeted.
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