I only play in real life with the cards I have.
So are there different rules documents for playing, for example Towers Standard vs Open vs Standard? Some stuff on the later cards doesn't seem compatible with earlier cards
Could you be more specific about the old and new cards?
Fellowship block doesn't have any cards that reference later concepts like initiative and threats, but you can use Fellowship block cards along-side cards from later sets that use both mechanics.
Companions from sets 1-10 do not have printed resistance except for Sam and the ring-bearers, but when the resistance mechanic in set 11 was applied to companions that will never be ring-bearer, they ruled that all the previous companions had resistance 6 unless otherwise specified.
The unloaded keyword "ring-bound" (and the default unbound) were added in TT, and Decipher declared that all Frodo and Sam companions are ring-bound, but the other Fellowship block companions are unbound.
New shadow cultures were introduced in set 11. You can mix the cultures in the same deck, so you can use
and
cards in the same deck just like you could use
and
cards in the same deck. The cards do what they say, so a card that just specifies the race "orc" will work on any culture orc (e.g.
Rumil EP can shoot
Goblin Scavengers or
Scavenging Goblins), but a card that lists a culture will only work on that culture (e.g.
Scavenging Goblins can get an
Orc Hammer to play on himself, but not a
Goblin Scimitar).