Removing brick walls under the stairs

I want to remove 2 brick walls under the stairs to make more room for storage.
One is parallel with the outside stringer ( circled red in photo) and the other is 90 degrees to that, about half way up the stairs. Are these load bearing or just gap fillers? Do I need to put extra support in when I remove them? House was built in 1950s mid terraced.
Also (circled in blue) I have removed this what seemed like a pointless wall. Are these studs doing anything or can I remove them without any added support? The joist meeting on the furthest stud seems to be floating, only nailed in on the top stringer, is this safe? Could I remove the first 2 without any issue