Reversing a case fan should not change temps too much?

I have 5 case fans on my pc, last week and yes it was cooler then I was getting 26 degrees-28 idle on pc then it died.



I bought an identical motherboard and reattached the cooler(same paste) but one of the 2 fans at top I changed from intake to outtake then it got temps of 31 degrees.



I thought I would take it off again and put new paste on and this time got loads of cpu spikes so 31 one second then 40 degrees(with a slight distorted sound from pc and at same instant a video I may be watching would pause for under a second)



So I took off again, and remounted it at a different angle.



So its 31 degrees again which I am fine with and I know thats nothing to worry about its just I was trying to identify why it was cooler before, yes I know it has been warmer weather the last few days but I open my living room when I wake up in the morning around 9am and do not close it to around midnight so sometimes I am actually chilly.



The only difference in the living room was the pc was on floorboards when I moved in then carpet was put down a few days later so could the carpet either be bad for airflow or did making one fan outtake when the rest were intake be affecting it?



Sorry for all my similar questions I just get curious for things.