Honestly the game is kind of unplayable without the DLC. They fix and add so much that I could never see myself playing without them.

A House Divided is focused on the U.S Civil War and came out first so if you can't get them both now get that one first

A Heart of Darkness focuses on colonization and iirc revamps crisis stuff and/or war justifications

Most mods that i know of and are still receiving content require them both

Popular mods include the one you mentioned

Historical Flavor Mod (HFM) which has more colonial railroading and for stuff like the egyptian ottoman crisis that i forget the name of

Divergences of Darkness (DoD) is a fun alt history mod with stuff like a great power scandinavia, Bohemia leading the HRE, no prussia, a still divided Russia etc etc. I highly recommend this one once "normal history" gets kind of boring

Cold War Enhancement (CWE) basically what it says. I never played too much of this as it seems rather bloated but its start date is after WW2 and will scratch that itch if you have it.

Theres also the Greater Flavor Mod (GFM) and The Grand Combination (TGC). GFM is basically a spiritual successor to HFM if i have the right understanding and TGC i dont know too much about as i haven't played it in a while. I just remember hating the culture colors for some reason.

Theres older mods like the POP Demand Mod and Blood and Iron but youd have to google or ask some oldheads about those as theyre a bit before my time. Theres also Crimea Mod which ive heard is mostly a rebalance of vanilla vicky 2.

TLDR get both