Lot to unpack here, first do my friends need my Mondrinth world gen mods to play hamachi with me?

Mods I'm using: Distant Horizons, Indium, Sodium, Noisium, and Tectonic.

Also - Can I make a realm and put all these mods on there (they're all for sure compatible with 1.21). Or can realms only run on newest versions of minecraft? Also, would I need to download these mods into the server or are they like client side?

Unrelated - My computer has 32 gb of ram, is giving minecraft like 24gbs bad? why is it by default set to 2, that's super low right?

Also, I appear to be stuttering every couple seconds, and I'm pretty sure it's because of my gpu and or my cpu being really high percentage. Even on base minecraft with no mods it does this and I do not know why.

SUPER UNRELATED: With Distant Horizons and a WORKING version of Bliss shaders, when i look up, the sky gets filled with whatever was below it.

THANK YOU!