I've just downloaded the iris compatible version of this mod so I can actually render stuff with sodium installed, but it doesn't appear in the moment or on the title screen anywhere like the version that doesnt support sodium does.

is there any way to fix this or do I have to uninstall all my mods and install optifine as hardly any of my mods work with optifine installed?

ohh ok I understand, thank you

All versions are compatible with Iris - you probably mean our custom Sodium version:
Because of Sodium's changes in chunk loading, rendering doesn't work with the official mod. Our developer has proposed a fix, that is pending for the official Sodium and provides adjusted versions on our download page.

TL;DR: You need both, ReplayMod and our custom Sodium. There is no bundle or compatible ReplayMod.

Also, please use our official support Discord https://discord.gg/5GR7RSb for future questions.