Do I need to install the 32bit and 64bit file?

I have downloaded,installed and got the mod working in my Steam copy of GTAV but I wondered if I actually need to install

ReShade32.dll
ReShade64.dll

Or not because it seems to be working without it?

I did overwrite files with the ones on this youtube video though:

The d3d11.dll from that download there is ReShade64.dll, so that step was already done for you. But I suggest you replace it with the most recent ReShade64.dll you downloaded from here.

Rightio ok thanks.